Newbie here, just spent all morning at work catching up.
And I must say, there is no chance, and I mean NO CHANCE that Jack will end us with Liz. Granted, the films have shown evidence that she's been having doubts over her feelings towards Jack, but she loves Will. She was going to marry Will, even after meeting Jack. I just can't see Jack and Liz together. Jack is too much of a free spirit to want to be tied down. The whole thing with Gibbs and Jack (with the strumpets) could simply be a parting of the ways for Capt. and First Mate. Jack then looks back because he is off on another adventure.
And the whole "Will Becomes The New Capt. of the FD" angle. Honestly, could anyone see it happening before these scripts came out. He could have stolen the FD while the crew were off attacking another ship. With Davy behind Becket, there could be a case for overthrowing the leaderless crew and taking the Dutchman. Doesn't mean that he's the new Capt. indefinably.
And on those scripts. Have they been authenticated? There could be 101 reasons for that script being leaked, so I personally wouldn't use it as a bible for who the film is going to go.
Although I did enjoy the possible plot lines, I do think you're all reading too much into some things. And Jack will not end up with Liz. Period.