Original Elite Four Returns

On top of most (if not all) of the Gym Leaders returning to their original posts in Pokemon: Let's Go, Eevee, it has also been confirmed that the original Kanto Elite Four Members will also make a return. This includes the likes of Lorelei (an Ice/Water Type Pokemon User), Bruno (a Rock/Fighting Type Pokemon User), Agatha (a Poison/Ghost Type Pokemon User), and Lance (a Dragon Type Pokemon User). Players will only be able to challenge the Elite Four after defeating the eight Kanto Pokemon Gyms, and they must defeat them in a row in order to face the league Champion.

At this point, it has yet to be revealed who the Kanto League Champion will be. If things remain similar to First Generation Pokemon Games, your Rival will become the New Kanto League Champion directly before you challenge the Elite Four. However, since Red and Blue (and now even Green) are set to make an appearance in the game, either one of them could easily be the Champion.