Ofc I wanna see Misty too, but it's un likely to her to appear.
I like Iris, she's fun. I don't understand why she havnt appeared yet...
In all fairness regarding Misty, she's more likely to reappear than May or Dawn, especially when, unlike their Contest stuff, Misty actually CAN visit another region without being forced to put her current quest off (Kalos and Unova lack contests, obviously). Not to mention next year is the 20th Anniversary of the Anime, so assuming it doesn't get cancelled before then, they're most likely going to have Misty reappear there, if for no other reason than to ensure the original group is reunited for the 20th Anniversary. Heck, there's even some new merchandising for Misty being released right now (Anime Misty I should add) by G.E.M., and in her Kanto appearance, no less, and it's not even the 20th Anniversary of the Anime yet, so there's little doubt she'll be making an appearance (there's no real reason to create those things if she's NOT going to appear in the near future at all, let alone have a fairly major role.).
As far as Iris, she's probably not going to reappear, not to mention I suspect the reason why she's not going to reappear has something to do with how they ended up wasted a character return on Dawn (who literally offered nothing new to the table with her return and literally lacked a reason to even BE in Unova in the first place, while May at least actually DID offer character development in the way of Dawn, and besides which got new evolutions, a new outfit, and actually had a decent excuse for her presence in Sinnoh, and Misty got a new outfit, revealed her Gyarados in the main series, evolved her Togetic, and actually had a reason to be present in Hoenn [aside from the fact that her sisters essentially forced her to postpone her goal]). Shame, really, because a character cameo actually would have been VERY appropriate for her in this case, unlike with Dawn.
@Mawa: That's assuming they even bothered to age Max to a 10 year old. Remember, Ash basically was confirmed in Best Wishes to still be 10, and this is despite the strong implications of his having aged, even in Best Wishes.
So far as the topic, yes, Misty definitely needs to return, and for a LOT longer than just a couple of episodes (try a whole season, like how they brought back Charizard). Quite frankly, they really should have brought her in during Best Wishes, especially regarding that World Conference thing. Would have killed two birds with one stone, in that it would actually advertise an element from Black 2 and White 2, and at the same time it actually would offer at least some closure to her goal of Water Pokémon Master rather than literally no closure at all.