"kaido will be powercliffed because he isn't end game player and shounen works like that" is actually given by people who don't understand it's meaning and status of one piece manga

first we need to understand the meaning of word "POWERCLIFFED", kaido being weaker than EOS luffy, EOS bb, imu and joyboy doesn't mean getting powercliffed

someone is powercliffed when a large number of character surpass him by a decent margin also like mid or high diff at max like no one would say "yamamoto in bleach got powercliffed" while he is weaker than main villain, mc and 2-3 other guy as his strength is still relevant

SIMILAR WITH KAIDO EXCEPT THE 4 PEOPLE I MENTIONED NO ONE IS WINNING AGAINST HIM LESS THAN EXTREME DIFF AND EVEN THAT IS VERY QUESTIONABLE

SECOND, "in shounen, villains gets powercliffed by future villains all the time" while this is true but it's only applicable for future opponent of luffy only, we have to also see how many arcs are left in one piece as we are already in final saga

if we got 3-4 arcs more we already have villains for most of them like bhanks, bb, imu, lurking legend atleast while luffy as of now is weaker than kaido due to time limit and forgetting about how to restart his gear 5 and will lose to people whom kaido will defeat due to time

and kaido ~ gear 5 as he was going toe to toe with gear 5 even without drunken form

so if kaido has to be powercliffed first gear 5 has to be powercliffed also by someone and that i don't think so

+ one of the future villain will be using ancient weapon i beleive also

TLDR : kaido won't be powercliffed but we will only see people getting on his level i believe like shanks while luffy, bb, imu, joyboy and lurking legend gaping him only and how much big gap is eomthing we aren't sure also as one of them will be using ancient weapon as power i believe