Note that I'm only focusing on things that actually appear in the original show's runtime, so everything there is most likely planned already. As for where every image here stands:
Queued: Cape Mario, Cape Luigi, Fire Mario, Fire Sonic, Sonic Wave (replaces medium super and will push the current one to heavy super)
Coming but low priority: Star Spirit Mario/Luigi, Super Sonic/Shadow, Fire Luigi
Everything else is most likely not making it