Windows 10 Mobile official release date was November 16, shows the lifecycle documentation. Now, Microsoft was planning to release Windows 10 Mobile as an OTA update to eligible Windows Phone 8.1 devices. This roll-out was expected in December, as confirmed by many of official accounts.
But now it seems that it is not going to happen on schedule and Microsoft has delayed the roll-out of Windows 10 Mobile to Windows Phone 8.1 devices. Now a Microsoft spokesperson has confirmed this to ZDNet,
This November we introduced Windows 10 to phones including brand new features such as Continuum and Universal Windows Apps with the introduction of the Lumia 950 and 950 XL. The Windows 10 Mobile upgrade will begin rolling out early next year to select existing Windows 8 and 8.1 phones.”
Knowing Microsoft the roll-out has now become quite uncertain. May be the issues Microsoft faced with roll-out of Build 10586.29 to non-insider Lumia 950 and Lumia 950 XL forced them to delay it. Microsoft has shared a list of first devices that may receive Windows 10 Mobile first. If you are wondering what changes you will see with Windows 10 Mobile you need to read our massive changelog.