I firmly believe that this is how the arc will end and how Luffy will keep the WG out of Wano.
The Two Main Arguments:
Narrative progression.
The admirals appear periodically at the end/beginning of arcs to give us a gauge of the MCs progression/level relative to the world.
1. SHs encounter Aokiji mid pre-time skip -> The SHs get washed and are completely outclassed
2. SHs encounter Kizaru late pre-time skip -> The SHs still get washed, something has to be done
3. SHs encounter Fujitora early post-time skip -> The SHs can somewhat hold their own, but it's still too early and we have to evacuate
A natural next step would be
4. SHs encounter Ryokugyu mid/late post-time skip -> The SHs can hold their own fully now and can fend off a marine admiral
The state of Wano and the emphasis on the lack of Forests
A very weird amount of emphasis was placed at the beginning of the arc on how the plants/vegetation and natural resources of Wano were being depleted by Kaido's factories.
Just defeating Kaido on its own isn't enough to return Wano to Prosperity.
Assuming that Ryokugyu has a plant/wood-themed fruit (Fujitora + his purple gravity clearly take inspiration from Madara, why not Ryokugyu and Hashirama?), we could very easily see Ryokugyu getting Aokiji type feats where he creates entire forests in Wano.
