Well, hate to burst the bubble but NWN wasn't meant to be a single player game. I do agree that some things could have been done better, but I personally didn't feel so "cheated" - I simply knew that this isn't "another BG serie". Other then that, if I was a Bioware 'el hefe', I would have requested to make at least a bit more proper ending - i.e. where you return to the Neverwinter and go to Castle Never and through the ceremony and all that. But oh well..
I don't know this for sure, but somewhere I did hear that some sort of "expansion pack" for NWN may be released somewhere at the end of the year. Maybe it will sort of move 'further' with the story, maybe not. Maybe chars can get higher level and what not else. But until official notification, I'd treat this just as a 'rumor', what it also is at the moment