Its my understanding that there's only two maps for the Survival mode. More maps would be appreciated and perhaps some more additions to gameplay (like how Nazi Zombies evolved) because from what I'm reading, aside from the charms of being a marine and shooting an alien, its pretty blah. However I haven't played the game at this point.
More multiplayer maps are bound to happen. Movie movie related skins would be awesome, but I think I read in an interview somewhere that there was a rights thing involved and they didn't have access to those characters. I don't know if new maps "inspired" by the films would be an issue; likely.
An extra story chapter for each species would be interesting. F.E.A.R. 2 and Prince Of Persia (and many others I assume) did it with some effectiveness.