If Coby was going to fight Kuzan, he’d have a moment with Kuzan. Instead Cobys big moment was hurting Pizarros right forearm while Garp sacrificed himself.
Coby ain’t fighting Kuzan.
If Oda was going to setup Smoker as the one to fight Kuzan, then Smoker would have been involved during Garp's attack at Pirate island.
The fact that Smoker wasn't even involved at all, shows you that Oda is not setting up a Kuzan vs Smoker fight at all.
Don't get me wrong I don't really care for Koby and I have no problem if Smoker does fight Kuzan, but everything that went down at Pirate Island involving Garp, Kuzan, and Koby is all being setup for Koby to be the one to fight Kuzan in the future.
There is also a reason why Oda revealed that Kuzan was formerly trained by Garp just like how Koby was also trained by Garp.
Smoker is the one that fans want to see fight Kuzan.
Koby is the one that Oda will actually pick to fight Kuzan.
Or maybe they both fight Kuzan together.