Interviewed by vg247 after the news of the decade partership between Bungie and Activision, Brian Jarrad has confirmed that
Halo: Reach the last chapter will be developed from the study. "Joining the Halo universe through Reach, but I can assure you that the study will pursue other projects associated with this brand." This news comes not a surprise anyway: remember that Microsoft has in fact created more than a year an internal study, called
343 Industries, dedicated just to the development of the next Halo. So the series goes on without Bungie.
Please note that Halo: Reach will be released in the fall Xbox 360 exclusive and that the multiplayer beta will take place on May 3 for those who bought Halo 3: ODST.