Meh, JJJ's got to prove he belongs in the rotation, same as Sully, and same as every other young guy (AB last year, Powe, Baby, etc). If he does a Bradley and essentially forces his way into the rotation, they'll find minutes for him. What they couldn't do is rely on a rookie and a second-year player to play a key role on a team with title aspirations. We'll be a better team if JJJ and Sully can contribute, because we need the depth up front - but we can't rely solely on them.
EDIT: And there isn't that much of a logjam. The bigs-rotation will be KG, Bass, Green (if he resigns), and probably either Stiemer or Wilcox. Melo won't play any meaningful minutes for at least a year, he's a project. There's room for either JJJ or Sully to carve themselves out some playing time, if they've earned it.