One of the reason for high trust on bitcoin is that the bitcoin owner Satoshi identity is hidden. If all of sudden Satoshi come in the public and his identity is revealed, do you think it will have a bad impact on the bitcoin price and it can dump? Or do you think that bitcoin price will pump on this revelation? Mind you that i am talking about the real satoshi, not the fake ones claiming themselves to be satoshi.
People would start seeing him as the "leader" of bitcoin. So if he saying anything about bitcoin, most of the people will follow and support whatever he says. Even if he is wrong, people would support him since he is the creator of bitcoin. Bitcoin would somewhat lose it's decentralization due to people following one person. And yeah, in the short term the price will have some impacts. Satoshi might be able to easily manipulate the market either with his words or with the coins he own.