I think I would have to bump Morneau down a level. To me a superstar is a player that even people who don't watch the sport know who he is. While he is an excellent player I don't see Morneau as close to that level.
To your list of those with potential but a long way to go I would add Baltimore's Adam Jones. Granted he will need to show continued improvement but with his performance last year and the early part of this year I believe he has shown the potential.