Halo 3: ODST was a pretty good success for Bungie, but there has not yet been any reports that the developer is going to be putting out more of these adventures for ODST. Basically, what this means is that he does not really have any motivation to putting out any new downloadable content for the game. The game was only a one time thing and is not meant as anything else at the time. However, we have not yet seen the last of those characters that were introduced by Bungie in Halo 3: ODST. In an interview with Bungie after the game had been released, the writer and the creative director, who is Joseph Statten, said a little something about Buck who is voiced by the actor Nathon Fillion.
“I can’t comment on any future plans for our ODSTs,” said Joseph Statten. “But it would be a shame if we made a game about the planet Reach — a place where Buck, the ODST’s squad leader, was known to be — and not have him appear in some way shape or form…”
So it is pretty much guaranteed that Nathon Fillion will be playing a role as Buck in Halo: Reach. It is just not said how big this role will be.