Good chances that eventually Zoro will have to make his own black blade in order to rival Mihawk. Or at least I like this idea. This could also be a reason why Oda decided to have Zoro leave Shusui in Wano (his former black blade, Ryuma sword). But since he didn't even bother to have a Zoro-Ryuma moment like Zoro visiting his grave at the end of Wano I doubt Oda will do something "so focused" like this and instead just bring out another power up mid fight like usual.
-Reach yet higher level of coc
CoO upgrade he will most likely take it to new level after fighting shiryu
His hidden sharingan in his left eye
Perfected ashura form, as overpowered as that ability i think it's still uncomplete