Sabo has his own plot, thanks Oda for this one since the Ace-clone thing would be quite right if not:
Not to mention, then he would have to go against BB too, who was the one that sold Ace in the first place. Oddly enough, Sabo's is new Ace only as long as this doesn't take things in Sabo vs BB direction, which should be direction then.
Anyway, imho It's not about the things that indicate Sabo vs Akainu: It's about the things that indicate Akainu vs Luffy, which are much more, and Sabo vs the WG.