Honestly depending on how lazy they wanted to be it wouldn't take much to create "completely new" enemies.
All they would have to do is create a new mesh & wire frame then copy paste already existing abilities & AI to it.
Not that that is what I want them to do, Quite the opposite in fact. I want new enemies with better AI, a wider range of abilities, faster yet lighter attacks and encounters that require actual thought instead of just zerker rushing them.
That or new utility skills (cross class profession specific abilities would be cool), new weapons & existing weapons being spread around more to existing classes.
Ideally we would get both new enemies and new skills but if I don't see some real new enemies then I'm going to start wanting some new skills because if all they do is copy paste a bunch of stuff then it becomes very redundant.