So if you look at movie 19's poster, you'll see that one of the major characters in the film will be this blonde woman with the blue dress who owns a shiny Mega Gardevoir. This woman is named Chymia. She's on the Ash gang's side in the poster, opposite to the main villain, Jarvis, and his team of Megas. From this poster, it seems like she'll be an ally, right?
According to one of the sets' names, "Cruel Traitor," it looks like Chymia, her Gardevoir, or both will later be revealed to be working with the main villain/have some sort of true villainous role in general. This could further be supported by the fact Volcanion is considered to be an ally of Ash for the movie, and the fact it is opposite to Gardevoir as the other featured Pokemon in the upcoming TCG set (even being referred to as a "fighter", which could give it some sort of heroic connotation, could further hint at this leaked spoiler.
Now I know what you're thinking:
"I don't know why you're getting hyped up about a Pokemon movie." Yeah,I'll admit it, Pokemon movies now aren't what they used to be, but I'm just interested in this because we never really had a Gardevoir with a villainous role like this before.
Still kind of wish we had someone other than Gardevoir be the other featured Pokemon of the set since we already had a shiny Mega Gardevoir card and would prefer to have some other Pokemon have a bit more spotlight.