Russ specifically mentions "4 years" in the email, so looking to the end of the year 2021. Let's go with that, then. Windows 10 Mobile (W10M) is officially supported in terms of updates until the end of 2019 (depending on the branch in question, see my chart in the various news posts, e.g. here), so by the end of 2021, the OS would have been out of support by a full two years. Now, I'm absolutely sure that Windows 10 Mobile will continue to run, in terms of booting up and starting applications (after all, Windows Phone 8.1 still works pretty darn well even now), but as ever, the devil is in the detail. And there are quite a few details to expand on here, in the table below.
I'm not worried about security vulnerabilities, note. By the end of 2019, the 1709 'feature2' branch of Windows 10 Mobile will have had over 20 updates, all of them addressing core bugs or vulnerabilities, so the OS will be about as secure as it's ever going to get at that stage. I suppose it's possible that some new issue introduced into the Windows kernel for ARM devices over in the Desktop world might creep into Mobile, but that's unlikely. Even more unlikely is the thought of any malware authors attacking Windows 10 Mobile specifically, since the installed base is tiny (a few million now?) compared to Android and iOS on Mobile and Windows or Mac OS on the Desktop. Multiplex two 'unlikely's together and you essentially get zero: Windows 10 Mobile will boot, work and be secure, even in 2021. Trust me.
However, things aren't quite so bright as we look across the full feature set, plus there's a sting in the tail below the table that dominates everything else in this article in my opinion. But first, the applications and services:
|Outlook Mail||Tying into Microsoft, Google, and other email servers/accounts, there's no reason why email shouldn't work just as well under Windows 10 Mobile in 2021. IMAP4, Exchange and even POP3 protocols should all still be appropriate.|
|Outlook Calendar, Contacts||As above, the sync of PIM data is all via protocols that are unlikely to break in the next few years.|
|Maps||Microsoft's Maps app will still work in 2021 and with relatively recent map data, but I can see a time when updates to this stop being pushed to Maps under Windows 10 Mobile. This may happen in 2020 when official support for the OS stops. So you'd miss out on roads built from 2020 onwards. Transit data might also stop working in 2020 - it all depends on Microsoft's activity in the Maps sphere. Ironically, if they don't improve it much then it'll stay compatible and up to date for W10M for longer!|
|Edge browsing||Web standards are changing all the time, of course. Web browsers on all platforms are being updated almost weekly in some cases. Edge was left behind, effectively, mid-2017, meaning that its support for PWAs (Progressive Web Applications) is half-baked, in that there's no support for 'service workers' and notifications. This situation will get worse as the years go by and as PWAs become the norm. As with IE under WP8.1, most web sites will return information and you won't be entirely in the lurch, but the web experience will be less and less complete.|
|Photos||Windows 10's Photos system is now mature and I can't see Microsoft breaking compatibility with W10M in the next few years - there's just no need, however much the company likes to flirt with '3D'!|
|Store and app updates||As I write this, we're seeing Microsoft announcing plans to halt the distribution of application updates to Windows Phone 8.1 phones in July 2019, a full two years after support for the OS itself ended. If we apply the same two year rule to Windows 10 Mobile then Store app updates will continue until the end of 2021, rather neatly. So no worries there, though we can only speculate as to how active the UWP app scene will be then - it could go either way!|
|Cortana||The development of Microsoft's assistant has lagged behind Google's and Amazon's offerings and I can't see it getting that much better. Still, it's not going to get worse and I'm sure it'll still work for the basics in 2021, e.g. "Hey Cortana, give me the latest headlines on Prime Minister Johnson and President Musk", and so on.|
|Office||Office Mobile is pretty fully featured for a phone-based interface, there's not that much more which could be added. Development for Mobile is already ceased, but it should still work just as well in 2021, I can't see anything breaking. Office file formats do change, but on a timescale of decades.|
|To-Do, OneDrive||These Microsoft apps and services are interesting in that they're 100% UWP and fully encompassing all form factors still. So they'll not only carry on working undtil 2021, but I expect further enhancements to the UWP applications. No doubt intended to help on other Windows 10 form factors, but for the next year or so at least, W10M will get the benefits too. At some point I'd expect changes to stop being pushed to Mobile, but probably not until after the end of the 2019 support period.|
|Skype||Skype has only recently completed a major revamp of its architecture, so I think it's unlikely to change again in the near future - Skype should carry on working through 2021 with ease. The UWP application will get updates, though the Skype team's plans on the client front seem to vary according to the direction of the wind, so no bets here!|
|Third party applications and services||
This is a leap into the unknown, of course, but it's a safe bet that the 'app gap' will get worse through the next three or fours years. The absence of many IoT or personal banking or payment applications is well known, but even stalwarts like Netflix (something which our family relies on) have been flakey under W10M for the last few years and I can see the platform being dropped from Netflix official support long before 2021. In the same app genre, again as a data point, there's still no Amazon Prime Video client, the BBC iPlayer 'app' is now just a web experience, and the cutting edge nature of streaming video and DRM means that the situation will only get worse as time goes on.
Still, Windows 10 Mobile is all about productivity, eh? True, but decent entertainment would also be nice. And the games scene under Windows 10 Mobile remains a pale (or late) shadow of what's on iOS or Android.
Even productivity isn't a given for that long, in terms of collaboration with others. Microsoft Teams has now effectively been axed for W10M, while Slack is a pale shadow of its client on other platform and is based on middleware. Third party applications offer viewing of Google Documents, but there's no way to do collaborative editing.
In summary, most - but not all - of what you have today under Windows 10 Mobile will still work in 2021, but you shouldn't expect much in terms of updates or improvements.
All of the above notwithstanding, however you or I choose to navigate the world of sometimes failing services, there's a bigger issue here that needs acknowledging and it's not software-related. Microsoft stopped manufacturing Lumia phones mid-2016 and so any Lumia 650 or 950 range handsets are already at least two years old as I write this. By 2021, the hardware will be five years old and falling apart, even with careful use. Yes, Alcatel sold some IDOL 4 Pro (IDOL 4S in the USA), but manufacture of these stopped in late 2017, so these too will be old, at least four years old. The most recent hardware is the Wileyfox Pro, low end but flexible, and this is very much still sold, though I expect this to be out of stock by the end of 2018.
In the Android or iOS worlds, there's a never ending supply of new hardware. If you can't re-buy (or get repaired) what you already have, in the event of failure, then you buy a newer model, there are always options. But the options run out with Windows 10 Mobile hardware. It's already almost impossible to get a Lumia repaired or to buy an official spare battery and it's only going to get harder. Take a Lumia 950 (say) to a phone repair shop in 2021 and they'll look at you as if it's from another planet.
In fairness, the Lumia 950 range (at least) are trivial to take apart, thanks to the back cover coming off, to loads of Torx screws, etc. So a DIY repair isn't out of the question - if you can find a source for any spare parts needed. But I think we're squarely in the area of 'hobbyist repairs' here, meaning that it'll be hard to trust a Lumia as a main phone in 2021 purely because it's hard to instantly replace or repair it if it gets dropped and broken.
The one glint of hope in all this has been that Microsoft would return to the mobile fold - literally - with a folding phablet, the legendary Andromeda project. This was scheduled for Autumn 2018 but put back until 2019 (at least) for reasons that even I had to agree with. But surely this will be out in 2019 in some form, making this article a little less painful. Surface Mobile, or whatever it becomes, will be expensive and a professional tool rather than a consumer smartphone, but at least for those with deep pockets it will be a way forward with Microsoft's OS, UWP applications, live tiles, and so on.
For many of us, of course, all of this is interesting but not showstopping, since I know many are experimenting with running an Android phone in parallel, usually with many of the same Microsoft applications and services. If a Lumia 950 or similar did take a tumble or suddenly pack up then it's best to be prepared and have something ready to take up some of the slack, I think?