Bungie's E3 announcement of Halo Zero is in the works or maybe Halo 4 or a new Bungie IP.

Halo Tournament

Multiplayer Based Halo :D

Kind of like how Unreal changed into Unreal Tournament :)

I don't think we'll see anything from them at this year's E3. A little too early.

well they are suppose to be co developing halo chronicle with peter jackson wingnut studio...... and i remember to have read somewhere that they were keeping there engagement on that matter even after they left MGS....

and about people talking about halo 3 I honestly think we won't see another halo FPS in long while....doing XIII version of a game is a Sony trend lol :) MGS proved they can come up with new IPs and I don't know if you noticed but most of them are just planed to be trilogies....