The thing is Oda can easily go Wano route with him and Sabo gangbagging Akainu.
Luffy Said many times he will take down Kaido too,didn't stop Oda for having a buildup on Zoro's involvement and potential killing of Kaido.
Sabo was surely brought back for a reason, given Ace's fruit for a reason just like Zoro inherited Enma and Oden's will.
Sure there was not that much buildup with Kaido for Luffy as opposed to Akainu but Postskip Oda has proved to make even the unlikeliest things happen.
Sabo may not have been there at the time but I think he has as much anger directed towards akainu as luffy.
Sabo has also been in Mariejoa lately,who knows he may have met Akainu in Marineford on his way out and that serves as buildup for a future confrontation who knows.
Anyways I'm keeping this in the back of my head until the fight but it will surprising doesn't atleast involve Sabo in that fight despite many things pointing towards that.
I don't really think that the Ace/inerithed will/Mera Mera arguments work if we are talking about a possible confrontation with Akainu. I don't see what they even have to do with Akainu.
In contrast, I certainly see the reasoning behind the Zoro/Oden inherited will (strike Kaido down and to open the Wano borders)/Enma arguments and what motivations tie them to Wano and Kaido.
I also don't think we have seen Sabo reference Akainu's name once (and the opposite as well).
I could see is Sabo encountering Akainu and/or briefly protecting Luffy from him before his fight with Akainu continues.
But him joining the Akainu fight still doesn't make sense to me, given all the elements I wrote about before.
We'll see.