Secondly, I'll stand by the statement (with a slight clarification). There is not one player you can point to right now and say they look like they have a good chance to make multiple All-Star teams at the major league level- the same way it looked like when we had four with Jay Bruce, Joey Votto, Johnny Cueto and Homer Bailey a few years back, or even last year when we had Mesoraco, Alonso and Grandal. Not one at the moment.
Billy Hamilton looks exciting but even in the upside scenario he looks like a speedier Luis Castillo, Deion Sanders or Juan Pierre. Without any power to speak of, it will be an uphill battle for him to be a multiple-time All-Star.
Daniel Corcino is the best pitching prospect in the system, but he really profiles as a #2 or strong #3 starter. If you had to project him now, he may make an All-Star team in his career year, but at his best looks like he is a slightly worse Johnny Cueto.
Donald Lutz probably has the best chance of any prospect at this point to prove me wrong, but he is currently on the DL in High A ball. He could do it, but if forced to make a 50/50 bet I'd bet against, given his age, position and development at this point.
Stephenson has the upside but it is far too early to tell. The point is I'd like to see more prospects injected into the system with his potential upside, which would greatly increase the chance of landing a potential future All-Star. I'm not complaining about the fruit that this farm system has bore in the past five years- it has certainly been plentiful. I'd just like to see that pipeline continue, as right now it is looking as bare in terms of upside as it has been in almost a decade.
Of the people you name, I will go out on a limb and proclaim that Mike Costanzo, DiDi Gregorius, Tucker Barnhart and Donnie Joseph will never be major league All-Stars. I'll be happy to be wrong, but I seriously doubt it.