maybe we'll be getting a lot more evolution card support. Wally and GPF are good starts so far, but we could get more cards with attacks and/ or abilities or stadiums that prevent all damage from attacks from basic Pokemon, like Pyroar, or Mewtwo lv. X in the D/P/PL sets. or go one step further and say if the Pokemon is not an evolved Pokemon, it can't attack, or use it's abilities and/ or ancient traits.
it could mean the decline of Pokemon EX cards, or just another experiment to make the game seem fairer, since EX cards have been dominant for a long time.