There will never be a Battle Frontier, PWT, or Unovas Challenge again, only ever more scaled back Battle Towers

There will never be a Postgame mini-region like the Battle Zone or East Unova again.

There will never be any new Pokeball types added like in gens 2-4 save one-and-dones like Dream Balls.

There will never be Puzzle Battles like Contests or Pokestar Studios again.

Transferring between generations will never not cost money for two different subscriptions again.

There will never be Spinoffs like Snap, the Stadium esques, or Mystery Dungeons again.