Update of Windows Insider App means that Windows10 Mobile OS rollout is around the corner
As of now Windows 10 is only available for the computers, laptops and tablets. For the smartphones only Microsoft Lumia 950, 950XL and 550 have the 'out of the box' Windows 10 OS most probably with build 10586.29 pre-installed on them. If you buy those phones, probably the first thing you need to do is to set up the phone and update the software installing the newer build 10586.63.
Is your Smartphone eligible for Windows 10 Mobile OS?
Then if you are the Windows Phone user with a compatible smartphone, in other words, the 'eligible' smartphone as stated by Microsoft, that has at least 1 GB of RAM and 8 GB of internal memory, then you have two options.
Either you can wait for the official build which is around the corner, or install 'Windows Insider app' and get the Windows 10 Mobile build 10586.63. You will then receive the stable build once the build becomes official.
Some reports are already coming out that in Poland the Windows 10 Mobile roll out has started. So if you have an eligible smartphone, you have just a few days to wait. Or you can install 'Windows Insider' and get the latest build immediately.
We have tried running build 10586.63 on Lumia 635 (512 MB) version instead of the 1 GB version of the same phone for which Windows 10 Mobile version was confirmed by Microsoft. And it works so smoothly and the experience is great!
As Microsoft has the goal of installing Windows 10 on at least 1 billion devices and so for not leaving out in the cold all the existing Windows phone users, learning from their past mistake of leaving out users like that and losing customers to competitors like Android and iOS, they would surely attempt to check and confirm the other devices' compatibility to get upgraded to Windows 10 Mobile.
That may take sometime because they first concentrate on the confirmed models according to this official list by Microsoft. Read more here List of eligible Smartphones for Windows 10 upgrade
Why 'Windows Insider' app got updated?
But if you can't wait, the new updated 'Windows Insider' app would be your automatic choice. This new Windows Insider App gives you the possibility to leave the program without resetting the phone and allowing you to use the stable version 'production build - Treshold'. This is necessary for those who are just experimenting the Windows 10 builds now but may not continue to be insiders once the stable version of Windows 10 rolls out for their phones.
Only the enthusiasts would continue to be the insiders even after the stable release of Windows 10 mobile official build.
There are many indications that the current build still named 'Preview build' to insiders could be the official version if there are not many bugs reported by the insiders. This is evident from the fact that the build 10586.63 was first released to mobiles and now the PC got the same builds. Similar thing has happened during the November update of 10586 for the first time when both the PCs and smartphones received the same version of the build.