well the sequel may be the marathon series, or a branch series, o even a prequel we just dont know yet. I dont see another halo gracing the 360 unless the 360 lasts until 2013 then it would come out in 2011 but if the refresh is 2012, i see the next halo being held in reserve to launch the next xbox, and given a long development time like the original to hopefully get the quality up there.
i would also go for a refresh of the marathon series complete with fx update and tie in that would be very very cool
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