I doubt they will ALL be Pokémon related. That’s not really how a double promotion works. He is most likely going to play songs from his album. Here is an excerpt from Rolling Stone:
“ Officially dubbed the “Pokémon 25 Version” of the song, Post Malone’s rendition trades the rootsy production of the original track for lush, echoing guitar and plenty of synthesizer sound effects that are reminiscent of the original Pokémon video game.
The song will be included in the setlist for Post Malone’s appearance at the Pokémon anniversary concert, streaming at 7:00 p.m. EST / 4:00 p.m. PST on February 27th.”
“The Pokémon team put in so much work -- this is one of the coolest things I’ve been a part of. There may be some surprises, too. It’s going to be a lot of fun.”
Definitely not much to go on, but it sounds like there is more!