Is it not plausible that the CIA was successful in tracking him down?
Nobody knows that but even if they have tracked him or even caught him, that will not make any sense because neither CIA nor FBI can shut the whole bitcoin down. There is nothing to worry about this issue but i am quite sure that satoshi is very good at hiding his identity.
The NSA is very capable of tracking your internet activity, however since satoshi may not have been targeted specifically at the time it is possible he could avoid monitoring by following strict measures to keep himself hid, if he did, then the only thing needed is for him to avoid using any of his old account and to never try to reveal himself to the world.