As much as I would love to see a sequel made, it's not gonna happen, at least not under the current conditions, and signing a petition isn't going to change that. Despite the rabid and loyal fan base Brutal Legend has (I like to include myself in this), it just doesn't have the numbers to back up statements like "the game is up there with Mass Effect and Call of Duty." That's simply not true, unfortunately. Mass Effect gets amazing reviews and sells far more (which I've never quite understood, I thought the first game at least was absolute crap and I haven't played the second one), and Call of Duty, jeez, don't get me started. Those games stopped being entertaining several years ago, but people buy them because they've expanded beyond just gamers, it's like a social activity now.
Now compare this to Brutal Legend-- several months after being released, the multiplayer went DEAD. Or at least for me, because I can't tell you how long I stood there waiting for a match. On top of that, it didn't sell particularly well, and the reviews, actually, were not 9-10/10, they were generally between 70-80%.
Look, my point is this-- I would love to see a sequel made. I would finance it myself if I could. I would sell organs to see this game made. Provided I got some creative input. But it's probably not gonna happen. You want to make your chances at least slightly better? Tim Schafer's got a Facebook page, go and let him know how much you loved his game and that you back it. Otherwise, it'll be a long time before we ever see a sequel, and to be honest, that sucks.