I don't remember them promising anything more than L4D how it was on release before anyone bought it. They promised updates quite a while after release, which did happen, people just expect too much.
I saw a video recently were they did say new maps, new monsters, new weapons and even new characters, but I dont really care for all that... all I care for are new maps and I think they will give us some more for l4d1 pretty soon
...i for one don't really mind if new maps will be added or not. i WOULD however love to see more SDK support. that's about maps. "new monsters, new weapons and even new characters"? - sure!!! bring it on lawl!!! that would be just sweet.