Oh, I have no trouble at all believing that we'll have more than 3 big leaguers matriculate over the next 3 years. My only point is that it might not be the guys you'd instantly think about.
Over the next three years Cameron, Drew, and Hermida will be moving on, and the impending FA lists for outfielders are fairly underwhelming over the next 2-3 years IMHO. I have little difficulty believing that Kalish, Ellsbury and Reddick will all get ample opportunities to prove that they can be starting players. Unless we re-sign Drew or sign Carl Crawford, these guys won't even be jostling.
V-Mart and Tek are both leaving next year as well, unless we get something done and the list of impending FA's at the catcher's spot is VERY weak. If we wind up in the same place re: Mauer and V-Mart as we did re: Holliday and Bay, I could see us promoting two catchers and basing playing time off performance. Expo is more talented than Wags, but Wags is much more seasoned, so I'm not sure which way that would go.