Bitcoin decentralization would receive a great blow if somehow Satoshi come back from nowhere. He would become something like Bitcoin CEO or ambassor, and decisions would somehow become centralized on him.
That's assuming Satoshi is still alive and participate on Bitcoin development/adoption. I fear more Satoshi's background/identity could be used to attack Bitcoin reputation.
This is definitely true. I also doubt that Satoshi would be able to at least influence the price by providing regulations imposed by him. That goes entirely contradictory on why he created BTC in the first place- which is financial freedom and control.
Assuming that Satoshi's identity is revealed, then I guess nothing big would impact. In fact, I also fear for his life since he may be the subject of all intrigues and searches when he gets revealed. In addition, I guess the price may also somehow affect given that his wallet address, up to this stay, still remains untouched containing thousands of BTCs.