I'd actually really like to see this show up again. I enjoy those few occasions when we get to travel with someone ─ especially in long caves. I don't feel so lonely and plus there's the bonus of having them heal our Pokémon as we go and maybe even give us an item or Pokémon at the end.
Seeing them again later is also something I wouldn't mind seeing. It would be nice to know they didn't just disappear after we spent that time traveling together. It would make their character seem like less of a tool.