WARNING THIS MIGHT BE A POSSIBLE SPOILER, FOR THOSE WHO CONSIDER IT ONE.
So i was looking through the achievements needed to get recon, all the Vidmaster achievements and i stumbled upon the Halo 3 ODST Vidmaster achievement called Deja Vu. It seems similar to the last level in halo 3 and halo CE where you have to race to the end of the level, also note the name of the level, Highway. So, is it possible that Highway is the last mission in ODST campaign where you have to race again? Now, this doesn't have to be the final mission, and in fact, can be a flashback of another ODST escaping somewhere, possibly to an LZ. As seen on the link, these achievements are unconfirmed so all of my theory might be wrong based on the validity of the achievement.
What do you think, please share your thoughts and theories.
And while you're at it, check the other achievements and you might discover the names of other firefight maps(again unconfirmed, the achievements are most likely fake so everything from me is just a guess))
[Edited on 07.26.2009 5:08 PM PDT]