Sweet - about time DC got going on something other than Supes and Batman. Wonder if it will be the old lineup, 80's lineup, or current lineup?
All the rumors that I have seen say it would be mostly the 80s "All-New" line-up - Nightwing, Cyborg, Starfire, Changling, Raven, etc. Much like the Cartoon Network version was, but with Nightwing in for Robin (due to licensing). Plus some "new" characters for marketing I'd assume.

They say that the "younger" Titans are all linked to "other" franchises (Robin = Batman, WongerGirl = Wonder Woman, Kid Flash = Flash, etc) so any hopes of a what I consider the real "Teen Titans" movie is pretty much out. Also would rule out a "Young Justice" movie for the same reasons...