Bungie has promised to work on Halo 3 for "probably" two more years.
The team had previously told us expansion ODST would be the final piece of added content for Halo 3.
"Halo 3 took two and a half years to make, and we're still working on it," said producer Allen Murray during the Bungie GDC panel (thanks Jostiq).
"We'll probably be working on it for two more years."
Whether that means there will be more DLC or expansions, or simply ongoing technical support, remains unclear. We're investigating.
The panel went on to reveal that a number of projects are in development at Bungie, but wouldn't elaborate. Considerable recent recruitment has made this possible for the first time.
Halo 3: ODST will launch exclusively on Xbox 360 this autumn. Before then, on 9th April, Bungie will launch the Mythic Map Pack on Xbox Live.