In an interview with GameSpy, Assassin Creed III's creative director, Alex Hutchinson, said Ubisoft didn't plan to invest in a "mouse and keyboard setup” for the PC version and went on to suggest gamers use a controller to play the game.
“We’re definitely supporting PC,” said Hutchinson. “We love PC, but I think it’ll be PC with a controller. I don’t see us investing hugely in a mouse and keyboard setup. I think if you want to play on PC and you want to play Assassin’s Creed, you have a controller.”
Ubisoft has since clarified his comment, telling RPS that it "will of course have mouse/keyboard support," the same as with previous games in the series.
So nothing seems to have changed, really.
Still no exact date for the PC version, but the console version lands in the fall.