Excerpt from Paul Thurrott Windows 8/Windows Phone analysis
Walk through that pretty Windows 8 UI and you'll see a bunch of familiar terminology, assuming you're a Windows Phone junkie like me. Live tiles sitting on a Start screen. A rich Lock screen with notification icons. A Windows Phone–like PIN password option (and an even cooler Picture password). Secondary tiles so that apps can pin "interior" functionality; an email app might let you pin a particular email folder, for example. Integrated search, for files, apps, and information inside apps. Location services. On and on it goes. The line isn't just blurring, it's disappearing.
Indeed, my sources tell me that the line really is disappearing and that the next major Windows Phone version, due in late 2012, will in fact be based on the Windows 8 code base. (Windows Phone 7.5 should ship sometime very soon and is a minor update to the initial version.) This too will have some interesting ramifications, if true, although I think it's clear that Windows Phone will evolve to pick up some of the improved Windows 8 functionality—better configurable live tiles, for example—regardless.