What will the Arbiter do now?

The Art of Halo Infinite depicts the arrival of the Guardians, the ruins of the broken buildings and the hordes of Brutes on Sanghelios.
These worries me.
Also, Rtas haven’t been mentioned in a long time. I had no idea what was going on about them. No new novels tell their story.
How eager I was to work with them again in the Infinite and fight off the Banished.