The theme of changing..or PERISHING (Spoilers)
Beckett's line about "pirates like Jack will perish if they dont change with the new world (revolution)" is quite true. In my opinion he means pirates as in cowards..they are cowards because they think only of themselves in times of danger..they will flee..and will fizzle out as a whole.
The only brave men in war are the ones who are fighting for those they love...the cowards are the ones who only care about themselves and their material possessions..and they flee..and often die straight away..this is why Jack needs Elizabeth in his life if he is ever going to survive in the future...
..Beckett basically says that he will need to change or die because revolution is coming and the change needed is obvious in movie 2..the change in his life is Elizabeth and love and the bravery he shows when it comes to protecting the one he loves
The Kraken and Liz was a wakeup call for him..he needed that moment where he was willing to die for Elizabeth He's done it once..he will DO it in the furure Smile He'll fight and he wont perish as long as he has her IN HIS LIFE..She is the change jack needs!