Seems doubtful, Lionhead have a deal with activision aswell as their deals with MS, I think even Dimitri is signed up to a publisher already, so it'd be a long long time before MS saw any benefit from this.
Plus Molyneux is no poor man, he created Lionhead to get out from under the thumb of one publisher trying to stifle his creativity (EA) he'd be unlikely to want to jump back under a different thumb.