I doubt that Kaladin will ever say the 5th oath. I think after/if he survives the next 10 days, he will want to go back to being a surgeon/leader of his support group. So there will be less opportunities for him to dramatically announce the 5th ideal. He wants to be done fighting, and although I understand that you don't have to fight to protect, when you don't fight, there's just not as much need for you to swear ideals. On the other hand, of course, this is Kaladin, and he never gets what he wants, so maybe ignore everything I just said.