Thurrott's new rumors, from a single source who asked not to be named, include some new specifics around both the UI and guts of the Windows Phone (WP) Blue OS. We've known since February 2013 (courtesy of one of my unnamed sources) that WP Blue would be a stepping stone along the way to bringing Windows 8, Windows RT and Windows Phone 8 into closer alignment around the NT core, programming interfaces and UI look-and-feel. Thurrott's source cites an interesting statistic (which I've not seen Microsoft state publicly), namely, that Windows Phone 8 currently has "33 percent API unity" with Windows RT. Supposedly the goal is for WP Blue to reach a (a very precise) 77 percent by the time it comes to market.
The ultimate goal, according to Thurrott's tipster, is to allow developers a single app that can run on both Windows RT and Windows Phone, thanks to universal binaries. That would fit nicely with the concept of a single Windows Store -- something to which Microsoft execs have committed privately to providing alongside the next major release of Windows (whatever that really means).
The same tipster told Thurrott that Microsoft is planning to do away with the Windows Phone back button in the WP Blue release. That's something I hadn't heard previously. It makes me wonder what Microsoft will do, backwards-compatibility-wise, for those of us who have Windows Phones that include back buttons as part of the actual handset. (I'd love to see Microsoft move the Bing search button to the left on Windows Phones, given it's currently far too easily to accidentally hit the search button on WP handsets.)
I'm thinking this could mean Microsoft ends up dropping the Windows RT name and instead goes for a single unified OS brand across devices. Whether this ultimately is called "Windows Phone OS" or just "Windows" (or something else all together) will be interesting to see. Whatever it's called, this branded OS should, I'd think, work on ARM-based phones and ARM-based tablets.