The bragging type will eventually brag enough to be caught. The only question is will he brag enough?
People claim all sorts of things on the internet, especially about their mad skillz. The hacker's not going to get "caught" in any meaningful sense unless law enforcement (who we've been told haven't received a report about the intrusion, the theft or the destruction of data) can prove that the specific person doing the bragging gained unauthorised access to the Bitcoinica server - evidence of that might not even exist after this amount of time.