I think people are going to be looking at a lot of old high cost fire types (hell, even standard charizard EVO doesn't look THAT bad with this), and as was mentioned Flareon-EX Turbo now looks truly terrifying instead of just a minor tech in some Volc decks.
A turn 1 attachment plus a turn 1 Kiawe plus a turn 2 attachment hits 170 damage on turn 2, choice band can take you to 200 against EX/GX. And actually you can hit more than that depending on how many elixirs you can land because Flareon can use flash fire to take energies from benched pokes. Theoretically you could have up to 2 flash fire uses on top of that for a total of 8 fire energy, which brings you to 210 base damage, 240 with choice band or 220 with FFB. With Tapu Lele, turn 1 Kiawe is going to be very easy to pull off, even easier in expanded with compressor.
I think a lot of naturally bulky cards are going to get steamrolled by all of the suddenly viable high cost, high damage fire type attackers and there will be more of a shift towards trying to make trades with lower HP cards... But Flareon has scaling damage so you don't need to invest that deeply if you don't need to hit those numbers unlike something like Megazard Y.
I also guess Lele will be around in literally every deck to punish people for investing too deeply with this kind of energy acceleration, but again, with Flareon you don't necessarily need to go balls to the wall with 5+ attachments on one card if there's no high HP threat to chunk through.
