Yes, we know of 24 players, but I doubt Nintendo stops there. My friend thought he saw a wonder seed, so we speculated. Since the seed changes the stage, what if Nintendo's way of showing off the new 2.1GB SSD read speed like Rift Apart for PS5 is to get a wonder seed, and it changes up the stage on the fly without loading, even if temporary.
They only showed a teaser so of course they are not showing all the cards yet. What are your guesses?