I always think the final of one piece would be: first lodestar and laugh tale (the race for one piece), and after marie geoise (final battle)
As two different events
As two different events
Imo, Whitebeard said it best: Once One Piece is found, then the WG can be brought to its knees. This entirely suggests that BB/Shanks cannot be endgame, unless of course they have larger motives than PK that lead them to the Mariejois area.
Imo, Akainu and Im are not leaving their respective locations. In the end, between those 2 and BB/Shanks (i.e. if they take One Piece or have a deeper motive shift), Mihawk will just be there to fight Zoro, regardless.
This is why even while I mention Shanks may not be endgame, he actually might be considering that out of any current rival faction, Ben Beckman is not even a sword user (compare to Shiryu, Fuji, and Ghandi), which is why I can imagine Mihawk being present for Zoro if Luffy ends up fighting Shanks in the end.