Worstgen
Cinera
Depending on which of the above he does, I could see Zoro end up anywhere from mid high tier (beating Kyoshiro) to low top tier (replicating/surpassing Oden's feat vs Kaido).
Cinera
If I were to hazard a guess, I'd probably go for somewhere in the middle, but of the two extremes, I find the upper bound more tempting.
Cinera
Oden was indubitably a swordsman, and one of exceedingly high skill. It seems Oden was at least a high high tier and potentially a low top tier. Zoro inherited Oden's sword. It was mentioned that Oden failed to make Enma black, and speculated that perhaps Zoro could do that.
KiriNigiri
Have you been binge reading the arc?
Cinera
I find it plausible that Zoro surpasses the swordsman whose sword he inherited in the arc relating to said swordsmen. One way for Zoro to surpass Oden would be to make Enma black, another way would be to give Kaidou a more grevious wound than the one Oden delivered.
Cinera
If Zoro surpasses Oden it seems more meaningful that he does so during the Wano arc than post Wano. There would be little narrative impact to surpassing Oden post Wano as none of the people with the context to properly appreciate the feat would be present.
Cinera
If Zoro blackens Enma but does so on some later island, the impact would be greatly diminshed as no one would recognise the gravitas of such an accomplishment. If surpassing Oden is to happen at all, it would be much more meaningful if it happens on Wano than after Wano.
KiriNigiri
Well, until Oda elaborates on black blades, I'm not sure if it will be the ideal way of conveying Zoro surpassed Oden. I believe he has to replicate or surpass Oden's feat, otherwise, his strength in relation to Oden will always be in question.
Cinera
For this reason, I find it plausible that Zoro surpasses Oden on Wano (perhaps by more severely injuring Kaido than Oden did). If this happens, it seems like a low top tier feat to me.
Cinera
I admit that I may have an optimistic bias as I would prefer it if Zoro left Wano a low high tier than a high mid tier.