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I don't know how slow I am for realising this (probably REALLY fucking late since I haven't been here in a long time) but Shota is from Hoenn and has a Bagon, and they have/still are promoting ORAS. Zinnia is a trainer who has a Mega Salamence from ORAS that ties into Delta Episode.
I am not saying that Shota is the stand-in for Zinnia since they look and act very different, but I wouldn't be surprised if Shota ends up with Mega Salamence instead of Mega Sceptile. Especially if Ash ends up using that thing, assuming he doesn't get one of his other pokemon to mega evolve.
Though I think even if Ash doesn't end up mega evolving one of his pokemon, I think Shota's chances of getting Mega Salamence is higher than getting Mega Sceptile considering the relevancy of the Delta Episode to ORAS.