Shaderhacker: I'd love to see Geralt go up against some really awesome monsters in his future quests. Vampires, werewolves, zombies, mindflayers (ok, that's D&D but still) and other such undead to use his silver sword against.
Are there zombies in the Witcher universe? I mean, drowners are kind of like zombies, if you think about it. You have to be careful with what you add in though, because you can completely destroy the mood and focus of the game by being like, "Rawr, random zombie/vampire/random other generic monster encounter!"
It's like the last Resident Evil movie--you can't just add in random monsters without having a reason for them being there, and the amount of explaining you'd need to do to explain why they're present would completely suffocate the main story.