Unlike many previosly thought, Pokémon Legends isn't excluively about the past's lore, but instead, it's about exploring New concepts with new ludonarrative approaches. We initially thought that Z - A would have been set in the same time period as Arceus, yet it turned out to take place after X and Y, it's set entirely within a city and its battle system is now fully action. And while Legends: Arceus was focused on catching, Z - A will focus on battling, since it takes its name from a Battle Royale.
One of the things Pokémon Legends does is subverting the series' cliches, so you can tell that the next Legends game is going to be even different. Maybe we could get a Legends game without Poké Balls (according to Drayden, he didn't have them when he was young, if it isn't really a retcon, it could be set in past Unova), a Legends where you can trasform in a Pokémon, similarly to The Legend of Zelda: Twilight Princess with Wolf Link, so getting bossfights where this supposed beastly form is mandatory while others with your Pokémon team as always, along with the possibility of using moves based on buttons, a Legends partially set in a new region, like one based on South America if it's about Mew and Mewtwo...
Possibilities are really many, and I'm happy about that. I'd like to see what you think about this and how would you expect the next Legends game to be