This E3 you will definitely be hearing about a Switch Pokemon game. I dont know if you will hear about the mainline one but this one will be announced during Nintendo's presentation and it's a doozy.

"Pokemon Battle S!!"

It's a digital only Switch game that will go for about $8 and its basically a combination of Pokemon Stadium and Pokemon Bank. It can connect with the 3DS games and Bank and you can store copies of your mons from your boxes (but do nothing else with them) and create pretty much any team out of them. the game only has a few pre-programmed trainers to fight since its made with multiplayer in mind. You can use your 3DS as a controller or local play with up to 3 Switches (PBS will support the new games)
The game has remixes of pretty much every battle theme in Pokemon history. No kidding. Theres stuff from Colosseum, Pokepark and even the typing game in this. It also borrows iconic environments from many Pokemon games to fight in. My favorite is White Treehollow. It was really made by people who love the games.

Of course the main thing is the graphics. Its gorgeous. Think Battle Revolution but made for the Switch. It looks better than the upcoming Switch games.

So enjoy E3. (No the pic is not an actual pic of the game)