There's still around 130 episodes to go, so....maybe? Did Carrell or Krasinski appear on Office Ladies yet?

Yes. They go episode by episode with some cast members like Russ and Daniels dropping by occasionally. They do standalone hour interview episodes with Daniels and Russ that you can listen to instead of the recap episodes.

Always possible. Of course, people have their reasons for why they do or don't do things.