From the oroginal Microsoft blog post:
As a part of our Windows device life cycle, Microsoft Store will soon stop accepting new apps with Windows Phone 8.x or earlier or Windows 8/8.1 packages (XAP and APPX). Soon after that date, we will stop distributing app updates to Windows Phone 8.x or earlier and Windows 8/8.1 devices; at that time, updates will only be made available to customers using Windows 10 devices.
- July 1st, 2019 – Microsoft will stop distributing app updates to Windows Phone 8.x or earlier devices.
- You’ll still be able to publish updates to all apps (including those with Windows Phone 8.x or earlier packages). However, these updates will only be made available to Windows 10 devices.
Now - again - this is all fairly irrelevant for WP8.1, since all 8.1 applications in the Store are essentially 'done' and anyone still using 8.1 certainly won't be expecting new features mid 2019. It's more relevant for Windows 10 Mobile, since there are some titles which never made the jump to UWP status for Windows 10. The blog post makes it explicitly clear that updates for 8.1 apps can still be pushed to Windows 10 Mobile users, but the pool of people still using 8.1 application under Windows 10 Mobile must surely be diminishing fast now and you have to wonder how much enthusiasm remaining developers will have.
This date also ties in with other public statements from popular 8.1 apps. For example Whatsapp, which has said that from today its 8.1 application 'may' be withdrawn in the Store, even for Windows 10 Mobile users. Unable to issue updates to its core Windows Phone 8.1 userbase, security issues may well force Whatsapp to pull out of the ecosystem sooner rather than later.
So - data points welcome. How much do you rely on legacy Windows Phone 8.1 applications on your Windows 10 Mobile phone? Is this update cutoff date a big deal for you?