The way I see it there are 4 options:
1. Kaido and Linlin both go down this arc. No questions asked. Multiple people take them out, its a big deal.
2. Kaido goes down this arc. Luffy gets help in the matter (aka, it wasnt a fair fight at all, so he's still poised to be weaker than a Yonko). Linlin survives to Elbaf and is the main villain there. Luffy 1v1's her there.
3. Linlin never actually gets taken out. She becomes an ally or some outside factor just prevents her from being truly taken out by Luffy. Maybe someone else does the deed in the future.
4. Both Kaido and Linlin survive Wano and the whole arc is a big farce

(Luffy's main battle is with someone else under Kaido)
What i don't see is Luffy soloing Kaido and Linlin together alone or I see him soloing Kaido one arc, then soloing Linlin in another. They are pretty much equal in ways, so there really is no growth involved in taking them both out alone, nor is Luffy strong enough to beat both on his own.