It's safer for them to stay under the protection of the Adarkim. The Khan agreed to it. Not going by Avagnar is for the best. I think in the Endwalker patches she might finally return to the Steppe and tell her brother to go through with it...if he wants to. She'll support him, but she won't stay.

It's up to him. Does he do it? Well...maybe. We'll see how I feel later on :)