Late last month, Microsoft previewed Windows 8.1 at Build 2013 conference, though there was no mention of Windows Phone 8.1. Rumors though have started surfacing about the next version of Windows Phone OS, tentatively called as Windows Phone 9. According to UnwiredView, Microsoft is reportedly assembling a new team to build an entirely new Windows Phone OS from scratch, instead of just updating Windows Phone 8.
The report mentions that the aim of this new team is to go back to the drawing board for the new OS and create a single version of that will work on both smartphones and tablets. The Metro UI that we see on the current-generation of the OS could undergo a massive overhaul or be scrapped all together. No details are available at the moment as the first draft is yet to be sketched, and it is obviously too early to comment on what devices this new OS would be compatible with.
The team is expected to present the first ideas later this year to the Microsoft executives, with the OS likely to be unveiled sometime in 2015.