That's no big secret. The same thing is happening all over the computing landscape. Oracle, for instance, is very loudly touting their latest database product as an Internet File System. It understands other file systems like that found in Windows and tries to overcome legacy issues by having everything happen on the server. They hope this will make thin clients more attractive, of course but they've acknowledge that morbidly obese clients are going away any year soon.
Similar efforts are in motion from numerous other vendors.
Since Microsoft deals more heavily in the client end they have more of a legacy problem. This is probably a greater source of anxiety than the DOJ for Redmond. How do you make any big improvements without losing large chunks of user base along the way. I think the choice of Outlook is a big indicator of the strategy. The PIM and messaging client is the closest thing to a DB system the majority of people will deal with first hand.