While it's possible that Oha Suta could be referring to something else entirely, the most likely scenario is that the show is where Pokemon Let's Go Pikachu and Let's Go Eevee for the Nintendo Switch will be properly revealed to the public.
This seems to point to more information on the upcoming Pokémon Switch game especially since Oha Suta called the news "shocking", which might have a connection to the leaked title Let's Go Pikachu.
The game is a mainline RPG set in Kanto and has brand new 3D graphics that haven't been seen in a mainline Pokemon RPG before. We know that Nintendo is going to show off the new Super Smash Bros game for Switch during the show, but beyond that, we don't really have any idea of what it will reveal.
Update: Pokemon Quest is available now for Nintendo Switch and will come to mobile at the end of June 2018.
While that one new Pokemon will be the only new Pokemon seen in Pokemon Let's Go, we'll also get some Alolan forms in the game. But before the Let's Go games were announced, I didn't have enough of a reason to participate; I mostly want shiny Pokemon for battles, and I like to battle in the core Pokemon RPGs. Let's Go, however, will only have local multiplayer. Instead, it's a new touch-focused game utilizing a voxel style that tasks players with seeking out rare treasure spread across Tumblecube Island, a place "where everything's a cube - including the Pokemon", according to a press release for the game. Pokemon Quest will let trainers explore Tumblecube Island with "a team of up to three Pokemon".
This story is developing.