>>39206702To be honest, I think its silly to assume that all the protagonist characters and rivals are by default going to have starter Pokémon
Hell we've already seen this isnt the case with characters like Blue having Pigeot instead of Blastoise, or characters like Hugh who don't use a traditional starter.
They don't have to line it up so that each generation has an equal trio of characters. We've never seen Kris appear canonically with a specific Pokémon before, they could give her literally anything they wanted and establish that as her main partner Pokémon if they wanted.