To be fair, Luffy was the one Zoro told, in detailed terms, that to stand between Zoro and his dream is to die. So Zoro referring to this promise is proper.
This, I think, also confirms my belief, if nothing else, at least Luffy will be there to directly witness Zoro vs Mihawk. The other SHs may or may not be there, but Luffy will be there to see it with his own eyes.