Ace wanted to face Blackbeard to avenge Thatch. Sabo will not have any business with Blackbeard in that regard.
The point is, it's not like Sabo will actively
pursue Akainu in order to avenge Ace. That's not the point. The point is, that Sabo, as Luffy's brother, may end up in the same situation as Ace, Luffy's and Sabo's deceased brother. Ace threw himself between Luffy and Akainu to protect his brother, dying in the process by Akainu's hand, after Akainu mocked his father figure.
Here, we might have a similar dynamics, with Sabo interfering and standing between Luffy and Akainu yet again, protecting his brother as Ace did, but this time not failing and fulfilling his duty which he didn't 2 years ago. Especially since Akainu has hatred towards Dragon too as the worst criminal, who happens to be Sabo's father figure.
From this perspective, Sabo facing Akainu would make sense.