The thing is, how do you replace Larry King? You don't. I would prefer they give it to someone a little bit edgy. Penn Jillette would be ideal - he's excellent when he's being serious (his talks on ReasonTV are wonderful), but CNN would not do that. I realize he's a left-leaning libertarian, but he'd be good. What's best? He'd get people to freaking think!
CNN doesn't care if people think. They care if people watch. I doubt Penn would be able to do that on a consistent basis, tho he might get a large audience if he were to interview Teller.