The foreshadowing for Zoro Killing/Defeating Kaido is pretty strong. I don't trust Oda enough to bet on Zoro outshining Luffy, but if I was one of the ZKK advocates, I wouldn't feel too bad if the Kaido fight ends up a Luffy show again. In this instance at least, Oda has gone to extensive lengths to set up Zoro's confrontation with Kaido.
Yasuie, Enma, Oden, Ryuma, the Dragon Legend and Zoro's own statements point to Zoro felling Kaido.
At the very least, the sceptics who doubted Zoro will even face Kaido are the ones who've been wrong so far.