Sure sure
Imo, while not allying with Shanks, the final war is gonna be a an actual bloodbath, and all this convinces me of is that the crew probably won't fight 1 particular faction at once. It could end up being that Luffy fights BB or Shanks or Akainu in the end (or all 3), but the same would apply to Zoro with Shiryu, Mihawk or Fuji/Kizaru. Maybe Luffy's final opponent is BB, while for Zoro it's Mihawk, as an example