Someone has gotten hold of what certainly appears to be a PC build of Far Cry 3: Blood Dragon, and uploaded video of it in action. Take a look, quick - the last two mirrors I found were pulled rapidly by Ubisoft.
Blood Dragon continues to look like a 1980's futuristic action film, apparently involving the destruction of Toronto. We still have no idea what platforms it's headed to, because Ubisoft's only official allusion to it was an April Fool's Day joke with a snippet of gameplay footage buried in it. It seems a lock in for Xbox 360 in early May, though.
"I'm not going to tell you where I got it from; I just got it from somewhere," our canny uploader remarks, doing Ubisoft's marketing work for them.