From the Microsoft post, which mainly talks about the latest update for Windows 10 on the desktop/laptop:
I know that a lot of Windows Insiders are eager to know what’s going on with Mobile builds. As you know we’ve already released the Lumia 950, 950XL, and 550 devices with Windows 10 Mobile preinstalled, and we’re still on track to release Windows 10 Mobile as an upgrade to existing devices early this year as we planned. The team is working now by looking at data and reports from Insiders who have upgraded their devices to preview builds, and ensuring that we deliver a great upgrade experience to customers. We’re excited about making the upgrade available, and will share new information with you just as soon as we can on how the rollout will happen.
We’ve also been working on our shared core which spans across PC, Mobile, Xbox, HoloLens, and more – which we call OneCore. Our build systems produce new builds daily for all of these editions, so as we’ve been doing this work we have been producing new PC builds as well as mobile builds. Today we deliver our 4th PC preview build, and are nearly ready to start sharing new preview builds for Mobile as well. We will start by making these builds available to devices that shipped with Windows 10 Mobile – the 950, 950XL, and 550 – and expand from there as we release Windows 10 Mobile to other devices.
This change in the way Insiders builds are made available doesn't surprise me hugely. In fact, I'd been amazed by the amount of attention given to people playing with Windows 10 Mobile on humble phones like the 630 and 640 when those users who'd shelled out £400 or more for the latest flagship were faced with bugs and issues. If I were Microsoft, the priority should be to get the OS stable and performing perfectly on the 950 and 950 XL. (Of course, since most of the reviews went out a few months ago, it's all a little like latching the stable door after the horse has bolted, but let's stay optimistic.)
Our editorial 950 is on the programme and waiting for the promised builds - rumour has it that 10586.71 is imminent. Watch this space.
PS. Thanks to Mobile Fun for the loan, see them for great Lumia 950 accessories!