Y'know, the other day I had this weird thought out of the blue. Chances are something like this will never happen, but I pictured Doflamingo telling Law (before he's taken away or something) the Mariejoie secret.
Now, I know Doflamingo is beyond pissed, his whole empire just came crashing down, and if he didn't want to murder Law and Luffy, he surely does now. So why would he do it? Eh, I think it would be cool if he said something along the lines of "well, guess it's just you now, and seeing as we're not that different after all, I might as well tell you some interesting things so you may bring about even more chaos in the New World."
Since Doflamingo likely won't be up to his shenanigans anytime soon, I could see him giving away such info just so he can hear/know about it later on, and rejoice with the news regarding the "uncoming wave".
I know it sounds cheesy, but if anything, such chaos/commotion on the seas could slow down Kaido's coming, and work in favor of Doflamingo... or not.