Nintendo and The Pokemon Company have revealed that a Pokemon Direct will take place later tonight. There’s no other information outside of the fact that it’ll last 8 minutes.
Whilst it’s pure speculation, it’s clear that a new Pokemon game will be announced. It could be possible that Nintendo would be getting a Pokemon announcement out of the way before E3, but it could literally be anything. It could definitely be a teaser for the previously rumoured Pokemon Stars on Nintendo Switch.
It is likely that with the success of Pokemon Sun/Moon on 3DS, Nintendo would be wanting to release one more Pokemon game on the 3DS, and that’s why they’re announcing it before E3, but we’re hoping that it is something for the Switch.