Its a bit early to say, theres not even a release date for the 360 version yet.  At the present its a 360 exclusive, its possible we'll see a PC version further down the line as we have with Halo 1 and 2 (I guess 3 will get a release sooner or later) though.  I wouldnt get my hopes up about the quality of any conversion though, the record on Halo games isnt that good so far.