I believe Rush will be in this season. It's just a guess. He disappeared a couple months ago for two days in the middle of the week. He told the audience it was a once-in-a-lifetime opportunity. He had already hung out with the Prez in the Oval Office. He wasn't visiting the troops in Iraq. The guest host said all breathlessly that "Rush is BACK from what he was doing!! I am sure he will tell you ALL ABOUT IT TOMORROW!" But that next day, Rush said he couldn't tell; he deserved a personal life; others were involved and he wasn't at liberty to say.
So I guessed that he got a chance to play himself or a character on 24. We will see if I guessed right.