As of March 31, 2012, Bungie will no longer host any Halo services on Bungie.net.Current Halo data will be transferred to 343 and, at that time, "all live Halo data will be managed by 343 Industries, and Bungie will no longer be able to update game stats and player service records, to host new user generated content, or to operate the Bungie Pro service." Using a peculiar bit of language, Bungie notes that "any replacement functionality" will be hosted by Halo Waypoint on halo.xbox.com.
Notice that Bungie doesn't mention whether or not such functionality will be replaced, though it seems unlikely that Microsoft would allow Halo's community features to disappear. They are, after all, a hallmark of the franchise. Because really, what's the point of playing Halo if you can't show off how awesome you are (or, as the image above illustrates, how funny it looks as your Spartan's limp corpse sails through the air).