I haven't had time to read more than a couple of posts in this thread, but Microsoft stepping out of mobile is simply absurd. It doesn't make any sense as a rumor. It's so inconceivable, that I am not even going to bother saying why.
Also, Paul Thurrott's track record regarding rumors/speculations, has been average at best. I just hope that when the Lumia 900 gets WP8 (or at the very least, some updates if not the full-fledged OS), people will remember what Paul Thurrott had posted about that. Remember that he said, not only none of the existing devices are getting WP8, but no kind of update towards Apollo whatsover.
Finally, his technical understanding of things is also average at best. He posted something along the lines of "if Tango has push notifications, then the Skype team is just making excuses by also not implementing it". This is something I fully expect from the average user, but not from a "high-profile" tech blogger. There are technical limitations in the case of Skype on Mango, and he just doesn't understand them.