As reported by Eurogamer, they say they had ‘no further plans for more Halo 3 content beyond ODST’, although they would continue to support the online Halo 3 experience with minor updates such as Matchmaking playlists and moderate servers as required.
Bungie stated: “We’ll never say never, but currently Bungie has no plans to make new Halo 3 content beyond the release of ODST.
With Forge and the Mythic map Sandbox we’re already seeing the community stepping up to create some great new maps and gametypes that will offer more variety and longevity to the game down the road.”
So, looks like the Halo franchise will have to move on without the mighty Bungie by their side.
Source: PR