They sure have measures to counter act this on new units. I think they should take a different pathway though. I have a PS3 that was mainly used as blue-ray player but I am not a gamer by any mean (in fact the only game I have is guitar hero). I follow the scene just barely out of curiosity and what strikes me from what I see on different forums is that people care A LOT about the possibility to play online with other players and sony ban to the game network is really the main incentive for people not to jailbreak.

To the point that someone got two PS3: one hacked for solo playing and one originale for networking!

It's a trusted computing type lock down AFAIK, so not software update-able. I think they can try the latter of your suggestions, but the same process could just be used to discover the new key, or they'd need to do some serious re-engineering.

then all the games out there that have already been sold wouldn't work anymore.