In Diamond/Pearl, instead of Misty and her Togetic coming back to show off the new evolution Togekiss, Dawn caught one instead. Instead of Jessie reobtaining her Lickitung, to evolve into a Lickilicky, this pokemon merely made cameos. So I don't think so.
Correct me if I'm wrong, but:
Misty made cameos in ADV, but no other series.
May made a cameo in D/P, but no other series.
Dawn made cameo in B/W, but no other series.
See the pattern? Iris will likely make a cameo, however.
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Like the games, the 3rd gymleader will likely be the one to teach Ash about megas, perhaps using a Mega Mawile. I imagine that this would happen before the gym battle against her (unlike the games), that way there could be a mega showdown.
There will likely be more than just 7 megas released in X/Y. I don't think we should limit the possible megas to just these, but if there are only 7, then Absol would be the most fitting.
MaX and MaY = X and Y
Hmmmm....
There is a chance for May to appear, especially if contests return in XY.
Hahaha, Hoenn Confurmed. {XD}