... if the real Satoshi would sign a message + move coins and tell the public, that they still haven't found the real Satoshi, wouldn't that put the real Satoshi's hidden identity at risk? Couldn't it somehow be tracked, if some 3 letter agencies would have let's say 50 suspected persons they are constantly watching for doing such a move and then just bust him?
There are rumors that 3 letter agencies run half the Tor exit nodes to track people using Tor. I don't know how they attempt tracking, if it works, or how successful they are, but those are the rumors I read. Satoshi extensively used Tor to conceal his identity, but that might be more difficult today with 3 letter agency involvement. Someone with his skill could probably find other solutions, but IMO the risk of having his identity revealed would be higher today than five years ago.