I don't think they'll put all of them in the Limited Test though, especially the new maps like Overpass or Italy. They may end up pushing some of the maps which stay mostly the same like Inferno (it's not getting a remake in spite of what some people think) or Office, but I think the rest will only be widely tested at launch. By testing multiple maps, but not all, they can still get a lot of data regarding where to look for bugs in the existing maps (like with the bench crash they fixed recently) so it will still be reasonably polished.

I think the more likely reason why it will take time is they're still working on a lot of features, I mean who knows how far along things like matchmaking and other game modes are.