DBGT: Does Goku die of old age when he turns SSJ4 in the future? At the start of Dragon Ball GT, Goku was turned into a kid by Ultimate Shenron when Pilaf accidentally said "I wish you were a kid again!" after stating Goku became way too powerful and he doesn't stand a chance against him now,  but would if he were to be a kid again. (wish granted, goku turns back into a kid)
During his fight with Baby, Goku turned SSJ4 and with it, became so strong that the magic of Ultimate Shenron could not affect him anymore. This was stated in the anime. He was too powerful for Shenron's magic to affect him.


After turning back into his base form, he became a kid again. He didn't go back to being an adult. So Ultimate Shenron's magic reasserted itself when he was no longer SSJ4.

At the very end of GT, we see the future. We see Pan being a very old lady, and a mini-goku and mini-vegeta fighting in the World Martial Arts Tournament. The mini-Goku was implied to be Pan's grandchild. Since we don't see them, we can assume that all of the Z fighters have passed away from old age. Goku is now walking around the tournament grounds, all grown up again in his base form, still having his tail (proving the wish wasn't reversed, because then his tail would have been gone) just before the end-credits come into play.


The question

If the Goku we see at the end turned SSJ4, would he get old and die?

If Goku hadn't become a child and grown up again because of Ultimate Shenron's magic, he presumably would be dead of old age by the time of the finale just like everyone else is. But as we saw before, if he turns SSJ4, Ultimate Shenron's magic wears off and doesn't affect him anymore. So is Ultimate Shenron's magic the only thing keeping him alive? Without it, would he become old and die like he would have if it had never affected him in the first place?
No. The wish was to make Goku a child again. When he grows back into an adult, the wish will not be in effect anymore. The youth he gains would just be a side effect of the wish. The wording of a wish is very important, as can be seen when Shenron granted the wish to revive everyone on Namek killed by Frieza and his henchmen. That wish didn't revive the people Vegeta killed because Vegeta broke off from Frieza.

Supposing the wish is still considered to be in effect, he still wouldn't become an old man when transforming. The reason he becomes an adult is to negate the negative effect of the wish on his power. Once he becomes an adult again, the wish actually has a positive effect because it is keeping him in his prime. During the Saiyain Saga, Shenron told everyone he couldn't use his magic to kill Vegeta and Nappa because they were too strong. At the same time, we don't doubt that Shenron would be able to make the Saiyains immortal if their plans to get the Dragon Balls succeeded. So, it isn't just a case of Shenron's magic not affecting people who are stronger than him. It is also a matter of whether the person wants to be affected. This can be explicitly seen when Porunga is unable to bring Goku back to earth after Namek explodes because Goku refuses.

If you recall, King Piccolo wished to restore his youth, but he was also stronger than Shenron, as evidenced by him being able to destroy the dragon. The wish still worked.

Also, just in case anyone is confused, all the examples I used were from the original Shenron and Porunga, but they should still apply to Ultimate Shenron. The only difference is that Ultimate Shenron is stronger, so it requires more strength (super saiyain 4 level) to overpower his magic.