I think there is a higher chance for Yellow to have an appearance in LPLE arc.
That's only if the LGPE arcs happen. Let's Go Pikachu and Let's Go Eevee is a fairly new and surprising addition for the Pokemon series however it's also the perfect opportunity to look back on what the Gen 1 crew and other Gen 1 supporting characters have been up to all these years. I don't know about you but if it does happen, I hope we get to see at least one hypothetically canon ship be turned canon or not. Honestly I don't even think marriage is too far off the corner, I mean let's be honest here. The Gen 1 crew are the oldest Pokedex Holders out of the rest, all of them being adults at this point, and they are not getting any younger as more and more Pokemon games come by, plus with the marriage trend going on in the shonen genre, I don't think it's that crazy not to happen. Honestly, I think it's more and more likely as the Gen 1 crew get older. However that's not the only thing I want to see in a possible Let's Go arc, I want to see how Red, Green, Blue and Yellow progress as adults. The manga has hinted several times that the Gym Leader and Pokemon Champion job is a side gig so is it possible we could see those four get full-time jobs soon? I can actually see Red being a Pokemon Professor, he is a battling genius with quick-thinking skills, like how he first guess Bulbasaur could use Solar Beam, so I don't think that's too far off. Same thing for the rest actually, Green being the son of Prof. Oak and Blue being an expert on evolutions. Actually I could see Blue working with Prof. Rowan, who is a PKMN Professor on Evolution. That should be exciting. As for Yellow I can see her being a PKMN doctor or even a regular doctor seeing how he patched up Red so quickly at a young age and likes to help PKMN in need. Your probably thinking she has psychic powers, doesn't need that but I'd say that psychic powers could help enhance her possible medical skills, not necessarily be it. Also their relatives. Seriously! We never seen Red's parents, we never seen Blue's parents talk once lol, and Green's parents, you have to think what kind of person they are considering how Green was raised.
On a side note, if we do see a Let's Go arc, what are the chances of Jessie and James made canon in Pokemon Adventures. Honestly I thought those two goofballs couldn't fit in Adventures but after seeing how competent they were in the training episode, I honestly think they can work as competent goofballs.