It's getting heavy promotion because of it's significance. I just believe in taking things in what we know versus over-speculating.
And Charizard returning for Best Wishes, Dawn reappearing in the same series (which BTW wasn't even given any prior announcements in any way), May reappearing in DP, Misty reappearing twice in AG, heck, Ash even revisiting Kanto for the Battle Frontier (actually, scratch that, ESPECIALLY Ash revisiting Kanto for the Battle Frontier) isn't significant? Again, all of those were about as significant as this (ESPECIALLY Ash going to Kanto for the Battle Frontier considering it was the 10th anniversary of the franchise AND it being the first time in nearly 10 years that Ash spent a significant amount of time in Kanto), and last I checked, there's barely even a peep regarding that (in Dawn's case, there was literally no news about it, certainly not on Bulbanews), not to mention they barely even treated it as being Kanto even when they DID go that route, not having any real references to Ash's old adventures besides Viridian Gym, Misty coming back temporarily, or Ash's Kanto starters reappearing.
And either way, use common sense: If they were only doing two episodes, they'd risk spoiling all the episodes before they even air, and that would be pretty stupid.
The two episodes where probably made in conjunction to one another. It'll most likely be just the two episodes for now, the show runners probably have a couple of episodes already set in pre-production. And, considering everything from planning to production to other episodes in the pipeline, It'll be a while before we see them in the show again (Not 12 years long mind you XD). I have a gut feeling they're going to be recurring characters at least in the SM saga of the anime.
The school setting might be a tad cliche, but as I've stated before, the advantages of said setting can not be overlooked. We've never had Ash in one place before, not always on the move going out to different places. The older characters can easily be written back into the show (in minor/supporting roles), since they can easily visit Ash or vice versa.
Perhaps recurring characters, though I'm still pretty sure that Misty and Brock, even if they are merely recurring characters (which in Misty's case would certainly be better than her being stuck in a gym since it implies she's resuming her Water Pokémon Master goal), aren't going to be dropped of with just those two episodes. For goodness sakes, with the amount they have teased as of late (and I strongly suspect that's not even the last of the promotion right now), they're risking spoiling the content of both episodes before they even air, especially when we've got less than two weeks before they air.
So far as the show, regardless of what advantages they might have, it's not changing the fact that Ash was short changed out of his goal, and besides which, that it's doing worse in ratings than even XY. Misty and Brock reappearing is probably the only real good to come out of this show (that, and the possibility of Ash's old Pokémon to be revisited).
I still think the information would've leaked if Brock and Misty were returning for more than the two episodes. Maybe they'll come back again later on besides these two, but right now it's just the two episodes. I could be wrong of course, but I don't really get why so many are thinking this is gonna be a more than two episode thing.
Technically, we don't even know of any episodes after these two at all, so we can't assume that they're only going to be there for those two episodes either. And as CodeHelmet pointed out, they're giving way too much promotion for Misty and Brock for it to be limited to just two episodes, ESPECIALLY considering that the prior special events such as the times Misty returned in AG, Ash returning to Kanto for the Battle Frontier, May and Dawn reappearing in DP and BW, respectively, and Charizard getting a reappearance in BW didn't get nearly as much fanfare as this (heck, in the case of Dawn, her reappearance literally was unannounced). And then there's the flashbacks to Misty and Brock dating from Kanto all the way to Johto. Correct me if I'm mistaken, but I'm pretty sure Misty during AG, not to mention May and Dawn didn't get any flashbacks whatsoever when they reappeared. I definitely know Charizard got a LOT of flashbacks when he reappeared in BW, though, and he managed to return for the duration of BW.
If I recall correctly, for the dub of these episodes this will be Misty's first official speaking role in the TPCi dub, since the last speaking role she had was back when the anime was dubbed by 4Kids.
I'm not sure if she was in Mastermind of Mirage Pokemon though, which was that testing ground for the TPCi voice actors.
She was in Mastermind, as the above user said. However, to be fair, we don't know if her TCPi voice from that special, or her TCPi voice from the Charizard flashbacks, will be reprising the role. They may pull a Giovanni and have Rachel Lillis reprise the role.
Saw the new preview, is it bad that I'm only hyped to see Jigglypuff back again?
To be fair, Jigglypuff arguably had been off the show for even longer than Misty did, so you focusing on it more than Misty or Brock's somewhat forgivable (I think the last time Jigglypuff appear was that Whismur episode back in AG.).
