Matt Soell has confirmed on the halo.bungie.org forum that Bungie's creating a new division to do the movies for their games.

Essentially, Joseph and Marty will be heading up a new team devoted to making cutscenes, trailers and the like (both in-engine and CGI) for Bungie titles.

This is cool because they get to work on them year-round as opposed to doing it all in the two weeks before E3. I'm expecting an increase in quality AND quantity.

Matt says elsewhere in the thread that the division will be concentrating on Oni until its release, so we shouldn't expect to see any new Halo stuff for the next few months.

Read the whole thread; there's a lot of info there.