Since Satoshi is an anonymous figure, what would stop someone from claiming to be Satoshi and then developing a new altcoin? Of course, if people think that Satoshi was the coin's developer then a lot of people will flock to the new coin. Perhaps it won't replace Bitcoin entirely but it could easily jump to #2 without any innovative features or technology behind it. Just the name would be enough. The Satoshi imposter could claim that he lost access to his old account or even his PGP signature and there would be no way to prove otherwise since he'd still be anonymous.