I got told that in this months PC ZONE there was a very small write-up about the fact the Ubisoft developers were worried that the control and fighting system may not be able to port to a keyboard. Also said that no PC magazines were allowed near the AC stand at a recent games show. Nothing is set in stone, but PZ are usually on the money, supposedly. You have to look at it from their point of view... to make the most money they make games primarily for consoles, and their games are always in the top 10 sellers list for that market. But they can't start abandoning the real gamers (pc), even if they do supply some disappointing ports.
But i do hope AC will be released for pc. My 360 controller is ready and waiting and it really doesnt take much more money for them to give it to us.