The lack of maps is something I've been concerned about from day one, given that one of the problems with Friday the 13th was that it only had three maps at launch all with the same theme, and it took Illfonic ages to add any more.
Certainly the three that are in this beta seem to show everything we've seen in all the trailers up until now, so it wouldn't surprise me at all if this was all there was in the full game. I hope there's more obviously, but I wouldn't be shocked if there wasn't.