My own feelings regarding the Halo franchise aside, I'm curious if this will be a 360 exclusive. Namely, if they are going to put it out on the PC. Microsoft has spent the past year or two puffing its chest, saying they want in on the PC market, but haven't really shown any commitment to those statements. However, giving their flagship franchise a simultaneous multiplatform release, or even putting out a PC version with a slight delay (moth or two) would go a long way to prove they mean business.
However, since all the MS talk about wanting to be a major player on the PC scene is just a bunch of crap to try and get someone to use GFWL, I doubt Halo 4 will be gracing any PCs any time soon, at least until we get a 360 emulator...