I don't want to see either of them ever again in all honesty, they've had thier time and now it's Dawn turn, plus neither one has a good reason to visit sinnoh so I don't see why they should, after all the only reason Misty went to hoenn was because of Togepi and with it gone now she's got no reason at all to visit sinnoh, not even for the new water pokemon as the battle frontier and her last hoso showed they can easily have her catch outer region pokemon around where she lives.
May doesn't have it any better as I just can't see her leaving her contest circuit to come visit either, So I say let em stay where they are and let Dawn have her turn in the spotlight.
Even though I'm not a fan of either characters I think I'd want May back for a few episodes. I'd like to see how she's progressed in contests and with her Pokemon. I don't want to see her come back as a full time character, think about it. It would be Advancedshippers V.S Pearlshippers, good lord.
I'd rather have had May never leave, but anyway...
I say both of them should come back to make cameo appearances, but as for permanently rejoining the cast... Dawn took May's role as the coordinator of the group, and for multiple reasons there isn't really any reason for May to replace Dawn. The writers have also been treating May like she hasn't existed ever since she left, so her rejoining the cast would make things even more awkward. Plus, if the writers were willing to have May rejoin the cast, why did they get rid of her in the first place? Also, May said she would train on her own now. Her permanently joining with Ash would be just as contradictory as her joining with Drew and/or Harley.
As for Misty, there isn't anyone who took her role away as a Water Pokemon Trainer, but why should she come back after being absent for 250+ episodes or so (not in a row of course)? I'd be annoyed if she just rejoined the cast just to be a side character (she can rejoin 250+ episodes later as a side coordinator but the coordinator of the cast, whichever one you want, can't be the main coordinator of the show?), so she should have to provide something new to the cast. (Brock hasn't provided anything new as a breeder, and look at what many people think of him.) But that brings about another question- what purpose would spring up for Misty to do that hasn't existed in 250+ episodes? And why does Misty have to do it- because she's Misty? Furthermore, Misty's not really going to be able to argue with Ash as much anymore since he's matured as a Trainer, and if that's one of the things people were looking forward to when they want her to come back, then... well... they'd be disappointed then.
Anyway, basically, getting Misty back in the cast is easier than handling her while she's on the cast, I think. And May got laid off and lost her job to Dawn, so her permanently joining wouldn't work. That's why I think they should just get cameos (*cough* also a certain other person should stay in the cast *cough*).
definaytly may. although she doesnt have any chance of returning to the main cast(she was in hoeen because she was in ruby/saphire) theres no reason for 2 coordinators on the main cast, but they should either:
1. bring may, drew, solidad and harley to sinnoh as rivals for dawn. they can have cameo appearences and compete against nando, kenny, dawn and zoey in the grand festival
I would choose Misty, but only if she was given something to do and given better water Pokemon and maybe one or two that aren't water type. May does the same thing that Dawn does, but I like the Pokemon that she was given in Battle Frontier. I don't care what any of you so called "May Fans" say, I just prefer Misty. May seemed like a crybaby IMO. I say, have an episode revealing Harley's "true" identity which is Misty dressed up as Harley to sabotage May, be on the show still, and not have anyone know. I rather have had Misty on the show in AG instead of Max; May could still be there, though.