I have always thought that even if the story of halo is finished, it could be continued in the form of a straight up MP game like unreal tournament.
Bungie knows how to do multiplayer and I believe that there is loads of potential for a multiplayer centric halo game, perhaps even revolutionary potential. Because across all three games the only big revolution in the multiplayer was online capability, everything else just kind of got tweaked. Halo MP could be expanded to a much greater degree.
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