Yeah it may well be a guest spot
You want Ash to leave? To me Ash IS the anime, to get rid of him would be awful! I have enjoyed watching his progress through the regions and I think Ash truly is developing even more as a character, heck he even looks older in the new trailer! Yes he does start of weak in the beginnings of the new regions, but that is what pokemon is all about, starting small and gaining experience along the way as he makes new friends, rivals and catches new pokemon.
I get what you mean about the 'reboot' though, that first battle with Trip's Lv5 Snivy in Unova was painful to watch!
It's nice that you would want him to get a proper send off though
Yes that is usually the case when Ash goes to a new region
But Brock did rejoin ash after a while in Hoenn, so I would say there is a slim chance!
It does look that way
If he is indeed in the next series, then we can pretty much assume he will catch some more!
Maybe he will get another starter pokemon like his mudkip in Hoenn, that would be awesome.
Which revealed pokemon do you think would suit Brock?