Why not. We close the end of the story. He has other things to improve post wano like his coo. Which an invisible and lightman will help with imo.
I don't see that at all. Zoro still has to fight a BB commander and then the Marines and he won't only improve his COO.
Luffy will likely tag team Kaido and that means that he won't be close to Yonko level. Zoro can be close to Shanks and Ray at the end of Wano too. Shanks and Ray are peak swordsman and don't have black blades, they have no DF, martial arts etc, just haki mastery.
To blacken a sword is a huge feat : only 2 uber strong swordmsmen can do it. Only 2, it means peak swordsmanship. Zoro won't be at peak swordsmanship post Wano, he still has some rooms to improve.
You can cut Kaido without black blade. So if Zoro managed to cut Kaido it won't equal to having a black blade. Cutting Kaido already will be a huge feat.
Black blade is too soon.