Full sets of leaks here.
All of these statements are 100% guaranteed verified.

1: New location is different than the old one.
2: Grass starter will have three stages, starting in first, and finishing with the third, final evolution.
3: The other two starters will be Water and Fire.
4: There are several new pokemon.
5: At least one of the new pokemon is humanoid (2 legs, 2 arms, standing upright)
6: One of the legendary pokemon that hasn't been named yet will be floating in some manner.
7: There is a new professor.
8: You will be able to fight other trainers (Some of which will be female)
9: You carry a bag which contains your inventory.
10: You get the pokedex very early into the game.
11: Multiple regions are playable in the game, including but not limited to snow, desert, and grassland.
12: The cover legendaries function as vehicles in the game.
13: Pikachu can Terastralize.
14: There are water pokemon you can catch in the water.
15: At least some of the pokemon you see can be captured.
16: Surprisingly, the games are going to be on a Nintendo console (This has been confirmed, Sorry Sony players, tradition is over)
17: Game is supposed to release this month.
18: There will be co-op of some kind.
19: You will be able to trade pokemon with friends if they also have the game and a switch.
20: There will be multiple types of pokeballs.

Also guys, I know some of these SEEM very unlikely, but as I said, they have all been verified, so please try and keep the discussion civil. Just because you don't believe it's true doesn't mean it isn't.