You never know, if they make Gen III re-makes they might make FRLG remakes too. Wynaut?
Kanto has somehow snuck its way into every generation:
G/S = Kanto was in the games
Gen III = Kanto is remade in FR/LG
Gen IV = Kanto is in HGSS
I wouldn't be surprised if Kanto comes back yet again....and leads to Ash having another quest there.
Return to Kanto definitely falls in box of possible scenario. When you think about it in all 5 generations Kanto and its game characters always managed somehow to find their way to appear receiving special treatment over other regions. Its also hometown region from where series main protagonist Ash originated from so its not so surprising if it receives more glorification compared to other areas Ash went through.
News of Jessie, James, Meowth and Giovanni returning back to Kanto leaving them on rather unfinished note is another factor which contributes to theory of filler arc happening in Kanto again. If we are lucky maybe Team Plasma finally makes their debut too,especially with upcoming release of Genesect movie.
Quest Ash could do during filler arc is already covered through BW2 games, giving writers lot of material to work with if they decide to do full adaptation of world tournament. Junior Cup was you could say prequel, some sort of foreplay, and creating several harder more challenging cups in context of world competition would be enough to create stable and structured storyline in same vein like Battle Frontier was before 6th generation comes out.
Perhaps there could be made tournaments based on elements like water, fire, grass etc serving as events to qualify for world cup.
Coincidentally appearance of older characters in new games also gives hope that we see Brock and Misty again for marketing and story purposes. I could see Brock easily returning to show progress as doctor if Kanto is revisited again, and Misty could go on journey to enter world cup tournaments advancing her goal of becoming water master learning new things and advancing skills.
They could lay role in TR arc(assuming activities from Giovanni continue)too, if Ash hometown region ends jeopardized.
Of course this is just speculation, because its unknown where continuation of BW series will be set. But for above mentioned reasons i think revisit to Kanto is on of more plausible options.
Maybe they'll make something up like in the Orange Islands when Ash needed to get the GS ball from Professor Ivy, hopefully that means they will bring back some old characters like Misty and Richie (man, I haven't seen Richie since Master Quest, that episode with Lugia) but that's just my opinion. I agree with everyone else's theory, though, Ash will probably revisit the Kanto, and get new clothes, but I miss his original clothes...especially his hat.
But I think Trips legacy will continue into Kanto, I mean they have made a big fuss about him and Kanto, I think he may change his mind in some way and end up there. Thats providing there is a small arc happening in kanto...
There's no "big fuss" about Trip and Kanto. All that happened was Trip called Kanto "the boonies" and used that as a reason to be dismissive towards Ash. It hasn't even come up since his first couple appearances.
There could potentially be a return to Hoenn due to a Gen. III remake in the games. But there's really no evidence for any of this.
They won't return to Hoenn for the same reasons they didn't return to Johto. There is virtually nothing for Ash to do there.
I'm not sure if I'd expect a return to Kanto, even with Team Rocket returning there. I still kind of expecting something like the Orange Islands happening, even though the chances of the writers going for their own region in this day and age sounds unlikely. I'm just not sure what Ash could do in Kanto.