Microsoft doesn't want to develop games for the PC. They know their Windows software will sell no matter what, and they get no profits from 3rd parties releasing games on Windows, so they don't care to promote it as a games platform.
They shut down Ensemble studios, (which was still profitable) because they want the Xbox, and only the Xbox to succeed. Even though Halo sold a gazillion copies on Windows, they still don't care for it to appear on their platforms. As long as Windows doesn't have any competition, they won't care. If MS were to control EA, EA would stop releasing PC titles.
<i>Well, EA's game sales have been WAY down, especially in the last year or two...</i>
EA is still worth about 8 billion I think. Left as it is, MS would need at least 6 years before EA pays for itself.
Consider that EA's most profitable franchise is the FIFA football series, and it sells like crack in Europe on the 360, the PS3, the PS2 etc.
None of this makes sense.
But both companies must be happy this rumor is flying, because their respective stocks are going up, albeit temporarily.