Let me start off by saying I like Geralt as a character and have no issues playing as him, however ...
I don't really understand why people need him so badly or the game "won't feel right" or whatever. The Witcher universe is such a fantastic, detailed one that you don't need one character to build a game around. The characters, the conflicts, the lore, it's absolutely fantastic and stands on its own even without Geralt there to drive the story along.
It's like Star Wars. You don't need to play as Luke Skywalker to take advantage of the setting and universe. The Witcher world is so much more than just Geralt.
Yea, Geralt's done more than enough, dude needs to rest and plough. I actually look forward to playing a sorcerer (we haven't really seen much of them) who uses swords or something.