Microsoft's Halo studio — 343 Industries — isn't even finished with Halo 4 yet, but the rumor mill is churning about the studio's next Halo project.
According to the Official Xbox Magazine's (via NeoGAF) rumors section, the studio is supposed to be working on a Halo 2 Anniversay game. If I would hazard a guess, I'd say it would fall in line with the Halo: Combat Evolved Anniversary HD remake, yes?
Other than that, no other detail has been shared. Now, keep in mind that this is entirely a rumor and from where we are in this current console cycle, it wouldn't surprise me to see this as an offering for the next Xbox.
Would you be interested in a Halo 2 HD remake? What's next, then? Halo 3 remade with Xbox 720 visuals?
