This is probably wrong.. but I have a ll' theory about this whole 'Is Jack dead!?'
Y'know how he does the 'honorable' thing.. Well, you never know if he is dead, after all, he basically ran into the Kraken with a sword, he'd probably stab it lilke 100 times on the way down to the belly or w/e. So he might've killed the Kraken, and lived. Either that, or the Kraken ate him or w/e. He could have died in many ways, but im pretty sure that Kraken is dead aswell. Someone tells me he isn't dead and will swim to the others :O
...If not, I wonder if the Black Pearl will be in the land of the dead? XD!