Green Bull coming to Wano seems likely… But just one Admiral against the combined forces of 2 Yonko? One of which is the "Strongest Beast", and can't seem to die?
Not to mention nearly all the Supernovas, and technically the 5th Yonko...
Sorry - but sending only Green Bull sounds like a suicide mission, and one asking for failure; even if he brings with him whatever super-pacifistas there might be.
Keep in mind, with all this crap happening in Reverie, I think the Marines and WG are going to be distracted for the time being, too. I think we are definitely getting the pro-oden revolutionaries and allies (Luffy, Kid, etc.) vs the Big Mom and Kaido forces, which will last us for some time. I'm sure we will learn some method of weakening Kaido... or maybe part of the stragey will become finding a way to get Big Mom and Kaido to fight one another again, since I think the chance of success against both of these forces is going to be very little... Even if the pro-Oden force is mostly focused on reclaiming the capitol and throne, and can probably take on Orochi's forces... The second Kaido and Big Mom's forces get involved, the chance at victory becomes basically zero without some new information. If Oda decides to just over-power Luffy from this little training session, I'm going to be a bit disappointed... If it were THAT easy to get THAT much stronger to fight Kaido, it's pretty anti-climatic. Maybe Luffy will be training pretty much the rest of the arc, a la DBZ?