He owns like $100 billion in bitcoin, so I think unmasking him as either someone who just has chosen not to use that money yet, or someone who died with the keys likely lost would presumably have a big price shock. Once he is identified, he and everyone connected to him becomes a massive target for organized crime and such, that many coins ending up in the hands of North Korea or something would probably significantly damage bitcoin's future; I imagine the feds would do whatever they could to ensure that can't be turned into spendable money.

if you believe the conspircy theory that Satoshi was created by an intelligence agency, then having it discovered would make a some people wary of using it.