To be honest, in GT episode 63, just before the final episode, a big change comes over Goku. Those who watched carefully might have noticed, but… In that episode, Goku, who takes Yi Xing Long‘s attack, sinks to the bottom of a deep hole. That is the turning point. Afterward, Goku still continues the battle, but what’s different from before is that he’s cloaked in an aura that won’t let any attack near him.
It might be that he died there, or it might be that he became something else entirely. I’ll leave that decision to the imaginations of everyone who watched. However, the Goku up to that point that everyone knows clearly does not appear after that.
In the world of Dragon Ball, Goku had already died multiple times, and up till then, each time he appeared with a halo over his head. However, I didn’t want to go with the usual concept of, “even when he dies, he comes right back to life”. I wanted the viewers to picture “death” in that way, and feel a sadness close to it in reality. So I had a “change” come over Goku.
And then after that, once he defeats Yi Xing Long and grants the final wish, Goku goes right off with Shenlong and the Dragon Balls, to somewhere that people definitely can’t get to. While wishing that people will be able to get by on their own strength in a world without the Dragon Balls. And Vegeta is the only one who notices where he’s headed.
Except, I personally go ahead and imagine… that Goku might unexpectedly show up, just at Chi-Chi’s, from time to time. Yes, unexpectedly….