In a new interview with Bungie, they speak on Halo 3 content. Well, apparently, the stream of Halo 3 content will end at Halo 3: ODST.
“We’ll never say never, but currently Bungie has no plans to make new Halo 3 content beyond the release of ODST,” Bungi told Eurogamer. “We will, however, continue to support the Halo 3 online experience with regular updates to matchmaking playlists and wield the Banhammer as needed.”
However, Bungie did add that “The future of Halo 3 online will become more and more defined by the people who play it”. I play it a lot, but I’m not very good, so I guess I don’t define it (sad face).