If Aokiji is the 10th Titanic Captain (I really doubt it) and if Aokiji is serious about fighting, and if Oda doesn’t introduce Law/Kid again to take him on, Zoro is going to be the one to face him. In that case, Aokiji is just another stepping stone before Mihawk.
That being said, I absolutely don't think Aokiji is the 10th. That would basically make him an Yonkou Commander and Admirals are not Yonkou Commander material as demonstrated by Ryokugyu.