I highly doubt that they would reveal anything of significance or even subtle hints. Since Magearna is a Generation VII Pokemon (provided with evidence that there was no game play leaks), I thought that Magearna would also receive an EX because they wanted to keep its Pokedex entry hidden, among other reasons they made it one.
Good point. Plus, to be fair, pokedex entries generally aren't indicative of gameplay or storyline.
For example, in Diamond & Pearl there was (unfortunately) never a plot of saving children from drifloons trying to steal away little kids.