I think if she has a cameo it will be the size of Barbossa's cameo in DMC. Maybe Will returns to land at the end and Elizabeth is waiting for him.
On another note, I was watching AWE yesterday and in the parlay scene Jones is standing in a bucket of water and it got me thinking why didn't Jack, Will, Barbossa, or Elizabeth just knock Jones over onto the beach? They could have knocked him out of his small bucket, rendering him dead or helpless, then killed Mercer, and taken Beckett hostage. Then if the EIC doesn't cooperate blow Beckett's head off and then fight the EIC.