Yep, Kaido is absolutely getting power cliffed.
God Valley flashback showed us that Kaido was the Jack of the Rocks pirates. Both in their 20's while the true #1-2 in those crews were in or close to their primes in their 30-50's.
If Jack (28) had good progression the next 31 years (Kaido is/was 59) then it's feasible he too would have reached yonko level around 4B.
But beyond that level there is the WB/Roger (and Xebec) level of 5B+ and we are yet to see how high Luffy, Loki, Shanks, Mihawk, Dragon, Sabo, Zoro, BB, Law, Kidd, Akainu, Aokiji will reach in the end. Some will "only" reach 4-5B, some will ascend to 6-10B. And you probably need to reach that 8-10B before you get to speak to Imu.