According to the wiki, them wishing for youth was just something that happened between arcs. It happened some time after Dragonball, but before the Cell Saga.
I'm going to have to keep reminding myself that even though Future Mai looks like she's the same age as Future Trunks, she's actually over 50.
Yeah, but main timeline has Super Dragonballs now. So if they really wanted, they could probably bring back all the dead people in Future Timeline.