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They'll bring the stones back. They can't just make a bunch of pokemon good for one gen and then take it away the next for no reason.
They also specifically nerfed Parental Bond when mega kangaskhan can't be obtained. They wouldn't do that if they never intended for it to be usable again (then again this is GF we're talking about, they also made Dark Void only usable by Darkrai, but on top of that also made it a shitty move.)
