Besides pushing out a PC Insider update as well as a cumulative bug fix for PC non-Insiders, Microsoft has shared a big of news regarding Windows 10 Mobile, Insider releases and future updates.

The new information is likely to cause a bit of a stir but is to be expected. Here is what you need to know:

New Insider builds (presumably the RS1 Redstone release branch) will go to the Lumia 550, Lumia950 and Lumia 950 XL first and "expand from there as we release Windows 10 to other devices."

and "expand from there as we release Windows 10 to other devices." Windows 10 Mobile general updates for Windows Phone 8.1 hardware is still planned for "early this year" but there are no dates to share just yet

Expanding upon the general Windows 10 Mobile update, Gabriel Aul said the following:

"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."

Regarding OneCore (Microsoft's term for a shared OS base), the company is prioritizing certain devices first, but moving all along the same path:

"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. "

Unfortunately, those still waiting for the Windows 10 Mobile official update are in limbo. It is coming, perhaps even later in February, but it sounds like there is still some testing and finalizing that is occurring. Considering the original plan was to have the update out by the end of 2015 and Microsoft is indeed pushing the update back further and further.

The upcoming Redstone (RS1) release for mobile and those update plans make more sense. Going forward, Microsoft is likely to focus on just its core Lumias released in late 2015 for future OS versions. Doing OS updates and testing on the dozen Lumia models out there is time-consuming and resource intensive.

Still, it's not all doom and gloom as Insiders of all devices will eventually get RS1 as well, just not as quickly.

Source: Microsoft