He doesn't have to look older, though, especially if they're doing the 1795 storyline.
Depp can look his age, but he can also look years younger than what he actually is. A couple of years won't make much difference in his case, I'd wager.
He's pretty, but he's rather striking, too, and it's about his talent. He has more of it in a strand of his hair than most actors have, period, IMO, and that's what matters most. If he doesn't actually play the role, there will be no words on this earth to describe my feelings of disappointment.