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.