My theories
Tia Dalma is the woman that Davy Jones longs for and was the reason he cut out is own heart for the following reasons:
1) they have the same heart-shaped locket (Hers: on the table in her hut while Jack is stealing the ring; His: while Will is stealing the key) And it is also etched on the DMC around the keyhole
2) her reaction to the "I heard it was the sea" "I heard it was the..." when she was telling the Davy Jones story seemed like she was miffed that the story had been embellished to more than it really was
So I think it will play out that she brings Jack back to life in the same/similar means she brought Barbosa back. Jack isn't undead because of finding the monkey's stolen coin for the same reason Elizabeth wasn't undead when she took Will's medallion. Jack has been given a reprieve by Davy Jones when the Kraken ate him... the "debt paid" line, assuming he's a Man/Octopi/Crustacean of his word. But Davy Jones is still a central character due to Will's father still having to serve his eternity.
Davy Jones and Tia will settle their differences somehow. Maybe that will free the crew of their servitude.
Jack will sail away with his true love, the Black Pearl, at the end. During the course of the movie, we'll see Jack's father, who just so happens to be the original owner of the Pearl, in a flashback showing Jack the tricks of the trade and telling him that one day the Pearl will be his, but then shortly after we'll see the Pearl attacked by Cutler Beckett, with Jack's father dying as the ship sinks to Davy Jones locker. Jack will then be taken prisoner by Beckett and branded, and then the scene will fade back to Jack being in the rumored purgatory plot line
Will and Elizabeth will still be married after Will realizes that it wasn't Jack that Elizabeth wanted, but the adventure of a "Pirate's Life for Me"
Then Mick and the rest of the Stones will sing the end credits Yo-Ho theme. Okay, that was just put in for the joke, because that would be too cheesy.