I've been playing MW3 just recently, in anticipation for the DLC sale on Tuesday. Hardly played it when it came out cos I got sick of the maps after beating Survival! Arkham City should be arriving on Monday!
Microsoft owns the Halo IP, Bungie left MS in 2007. As soon as Microsoft bought Bungie in 2000, they gained the rights to Halo. They can do what they want with it, so 343 *could* be developing a port of Halo 3 but I doubt it. I think they've had their last chance now; they could have released it to act as a jumping on point for H4.
I loved JSRF when I was younger but I've never played the first one so I'll probably try this on XBLA. From the looks of it, they have done a better clean up job than what they did for SA and Crazy Taxi.