If the SH are going to fight the BB pirates is Shiryu, if they gonna fight RH pirates then is Mihawk
Personally, i prefer Shanks revealed as a villain and he defeat teach contrary to everyone's expectation, and mihawk joins his crew so Zoro can fight him. (because surely the SH are not going to fight both crews).
I think Zoro will have just 2 more major fights until the end, that can be against one of these and against an admiral.