In My Opinion, its done for core gamers and MS does not care at all. they're just after a piece of Wii's pie.
as an example, when ME2 went multi-platform, MS's response was basically "We cant rely on 3rd party developers, here are some games by us, for the PC" and came out "Flight" and "AoE:Online" which will in no way interest many of us. maybe the hardcore fans i suppose.
seriously, in the coming year, other than Gears 3, what core gaming experience is it offering that its competition is not ? in other words, is there a good number of reasons to keep this console ?
and don't give me the "Halo sold a lot" response, were talking about promising future releases here.
best thing to do, IMO, is give them a bit of time, perhaps till the next E3. if their tactics are not changed by then, we can decide much easier.