I am asking this theoretically, and I am curious to see your opinions. We know that Luke failed to lift X-Wing in ESB. Later in RotJ, Yoda says that Luke needs no more training and learned what he needs. Is that also means he can lift the X-Wing with his force powers ? And this question is for only Return of the Jedi timeline, we all know that Luke, as a Grand Master, becomes very powerful later.
Did he or could he? I think he had the potential, for sure. I'm not sure he lifted it. Yoda did, though.
I say yes. Yoda says all that remains is for him to face Vader, which logically must mean he can now lift the ship using only the Force.
I also say yes. He didn't have any trouble lifting C3PO in front of the ewoks. Although an X-Wing is certainly even bigger and heavier, apparently if you're doing it right, that doesn't matter.
I want to expand on the great points that Hogarth Wrightson and SegNerd made. Yoda said Luke already knew all he needed. In TESB, Yoda thought Luke had the potential to lift the X-wing. Initially Luke was lifting the X-wing out of the swamp. Yoda said Luke failed only because he did not believe. By ROTJ, Luke fully realized what "size matters not" meant. He lifted C3-PO without even using his hands.
Yes. In TESB, Luke's character was impatient, his mind in conflict, he wasn't ready. By ROTJ, Luke seems more at peace, with a clear mind and a better understanding. He's far more zen like in ROTJ. At that point, the Force was his ally.
No. But at least he was a better pilot in ROTJ, because we didn't hear, "Hey Yoda, before you die... Could you lift my X-Wing out of the swamp again?"
Yes he had the ability to lift the X-Wing in ROTJ, as Yoda asked what more do you need to know, that you already know. So all he could learn from Yoda was complete, but he still had training to learn as he grew older after that, but essentially his training was over with.
Let's keep in mind, too, that in ROTJ we see the X-Wing parked safely on the turf outside Yoda's home. So either Luke was strong enough in the Force to guide the ship safely down, or he landed in the swamp again and was able to move it out successfully. Either way speaks volumes about how far he's come since the events of ESB.