There is no ironclad rule, but the setup so far points towards it. I think Shanks is falling to BB while Dragon will beat a Gorosei before falling to Imu in a 4/5v1 like Enel vs Zoro/Ganfall/Robin/Wyper. Anyway, lets see what happens.
It all boils down to what will happen first, Shanks interacting with BB or Shanks interacting with Garling. If the first thing that happens in the manga is the former instead then you bet your ass that Shanks will be involved in the WG war and die in it.