I'm afraid Young Link is gone. Not like completely gone, but grown-up. Young Link has had it's good times in OoT, MM, WW, etc. I could imagine Young Link returning to a Zelda game. Link can't always be Young Link. He has to grow up. Unless Nintendo decided there was too much Young Link on most games, that they probably decided to make Link all grown up.
Young Link is a very interesting character, but Link's young days must be over. Link can't stay young forever. I'm pretty sure some of us miss him, but we can't do anything about that.
I do agree that Young Link should return once more. He can surely pack a punch with his magnificent maneuvers with his sword. His Kokiri shield is the recognizable item in the Zelda games. Which I do miss that shield:3