If they're gonna let Arma 2 run on the 360 then it'll have to have lower minimum requirements than ArmA 1... unless some of the xbox optimizations from OFP:E in the engine carry over to the 360. Otherwise, it seems more likely to me that it'll be on PS3 than on the 360. Unless they yank the view distance down, or the texture quality, or who-knows-what-else.
I still think it's interesting that the depth of field postprocessing works better in OFP:E on my xbox than on my PC in ArmA with 5x the computing power ;p
[that's not fair, the latest patches for arma have allowed me to turn it back up, but still ;p]