I'm excited about it! To me, the series centers around Jack, so no Will or Elizabeth doesn't really bother me. After all, neither of them were really true "pirates" of the caribbean. Barbossa, yes. Jack, yes. The crew of the Pearl, yes. Davy Jones, yes. Will and Elizabeth? ...Not really. They just kept the story going. Now we have a clean slate with real, hardcore pirate characters taking the main roles. That's what I'd like to see for a change.
3D... well, I dunno. Might be good, might be a waste of time on their part. Frankly, I don't really see what they could do with PotC4 to make it look amazing in the 3D, like with Avatar or Alice. But then, might be as amazing as At World's End; we don't know.