What might happen to Bitcoin if its creator’s identity were definitively revealed?

He will be a Hero to many, and for some, a Villain.

He would be hounded for interviews, paparazzi would go gaga over him. There wouldn't be a TV show or Conference not vying for him to show up at. You can pretty much get the drift on the newly formed stardom of the this person. Advocates of Bitcoin would hail him. Protect him. Defend him. He'd be their Prophet. He would be revered by many.

On the flip side, you would now have a name to subpoena and/or call to as the creator of the system, and some lawyer would try to go all Tarzan on Satoshi Nakamoto. Lawyer X would picture himself on various magazine covers, "The Man Who Got Satoshi".

Depending on the nationality of the creator, the financial regulator may fine him/her/them or even try to charge them with making currency, which by law is illegal in many countries and then imprisonment follows. Remember Bernard von NotHaus and the Liberty Dollar? The government (especially the Federal Agencies in the US in particular) would just love to bring down this man. I wouldn't be surprised if the government moved all its machinery to do so, despite the positive claims and speeches that came from the Senate Hearings on the Bitcoin phenomenon.