The way I see it currently speaking Luffy is nowhere near as strong as an admiral much less Kaido.
He needs more training and to hone his skills and since we got a time skip recently, I see that it will be a trio effort of the big 3. No other way they can stand a chance individually.
>The Strawhats get split up
>The different constellations have to battle various underdogs to Kaido
>Everyone have problems eccept Zoro
>Luffy find some guys that needs his help and befriend them - they then help him get to / stall the big bad
>Everyone beat their opponents eccept Chopper and Nami that are useless and don't actually fight anyone. Lastly it's Luffy vs Kaido
>Gear (x) the shit out of him somehow, no plan just muscle against the strongest man in the world and for some reason this works.
>leave for the next arc
It will not be a straightforward fight obviously. Luffy went through enormous strain just to knock out Doflamingo yet Doflamingo is scared of Kaido and Kaido may potentially have the most durability of anyone seen in the series.
I can see Luffy defeating one Yonkou but another one + Blackbeard seems a bit far fetched if we consider that One Piece was supposed to be about 70% done during Dressrosa.
Gomu Gomu no Talk it is.
Gear 4 is powerful but he cant stay in that mode for a long while meaning any opponent that can outlast gear 4 can ein in a fight. I still see aokiji fit to survive although due to his analytic and defensive nature more so.
kaidou gets gamma knifed then moria steals his shadow and gives it to luffy, mr. 3 comes and gives nightmare luffy wax armor and invankov gives luffy a injection which gives him a short power boost and aces spirit materializes in luffy's fist as he uses gomu gomu no red king kong wax hawk storm
Gear Fourth is clearly meant to be his trump card at this point
The use of it on Dressrosa was in part a showcase of how utterly overpowering it is, in this case against a strong opponent who had no trouble dealing with him prior to using it. His issue is the strain it puts on him but it could very well be something lessened with time and more use.
It seems to level the playing field against characters that have been out of his league throughout the series.
Then how the fuck will be pirate king if he can't fight Yonkous and Admirals? Nakama help and ass pulls is not going to cut it. If Luffy is supposed to go from this point to the end to the end of the manga, he is very underpowered.
Unless Oda has a time skip coming up in the future, Luffy won't have enough power to fight these guys.
Gear Fourth can still be fleshed out to become stronger, utilize more abilities and, most importantly, not have as crippling of a side effect.
I think Doflamingo was just given too much endurance. It really was absurd how much punishment he took even if he was shaky after the Leo Bazooka. It downplayed the otherwise overwhelming power of Gear Fourth, something clearly designed to put Luffy on another level for the New World.
It makes a fight with Kaido look hopeless at this point if it happens relatively soon. Kaido being purposely built up as being nigh invincible is a bit strange though, who knows how the first Yonko conflicts will fully play out.
Don't forget before Gear 4th Donflamingo took massive damage from Law regarding his organs, a red hawk and getting electricuted by Law.
Gear 4th was heavily nerfed imho.
If Luffy is supposed to be the baddest man at the end of the manga, serious power ups is going to need to happen and since devil fruit mastery is needed.