It appears that Microsoft has registered several ‘Halo Infinity’ related domain names this week including HaloInfinity.net and HaloInfinityMultiplayer.com. They didn’t just register various Halo Infinity domains but also MoreThanJustAMap.com and SpartanOps.org.
Infinity is a Halo:Combat Evolved map (pictured above) that was exclusive to the PC version of the game. It is the longest multiplayer map and in the shape of an infinity symbol (∞). We currently don’t know anything about what the domains will be used for but it seems it may have something to do with the map (mostly because of the MoreThanJustAMap.com domain).
My completely out there guess would be an XBLA, one map (with forge capabilities) multiplayer only Halo game. I mean, they wouldn’t go through all this effort if it was just DLC for Halo Anniversary would they? Well, so far Microsoft hasn’t announced anything so all we can do is wait.
UPDATE: From information in the latest Game Informer that Spartan Ops is a multiplayer mode in Halo 4 that will be like the Spec Ops in the Call Of Duty games but with a storyline and carried out over several months and the multiplayer takes place on the UNSC Infinity, a 3km long ship sent into deep space on a mission and it contains a virtual reality sector that creates the multiplayer experience.