Are Jeff and Joel cashing out?

That doesn't mean anyone is cashing out. Eventually Jeff and Joel won't be running StackOverflow. At some point you need to hand off control to someone else or let the site disappear. (Long term here, people don't live forever) All Jeff is saying is that he is welcome back as long as Jeff has the power to give him his job back. Jeff can't promise a future owner of SO will honor an agreement made now.

Then again, it could just be a figure of speech Jeff tacked on. :)