I know that Bungie said that Halo 3 is the last Halo game, and it did sum up the story, but it just seems like there could be another one. and why not they would definately make money on it. so will there be a Halo 4.
They probably will, but not for a while. Bungie will probably move on to something other than a 1st person shooter after making them nonstop for 6 years. But I'm sure that another Halo will come out eventually on a different storyline.
last I heard bungie didn't want to be exclusive to micro anymore, also microsoft can't just tell bungie to make a game, if bungie doesn't want to make halo anymore they don't have to, bungie isn't making halo wars.
IMDB.com has had a Halo film slated for 2009 on their page for a while. Though this doesn't mean much, I think Halo video games may be a close for now. If the movie does well, there will probably be sequels. So, the story will probably go on, just in a new format.