He told me this past Sunday and said he thought he had few comrades left at The Nation. It is sad - and very bad news for the magazine. I don't think he's turned so comprehensively belligerent though. As for replacements, an audacious choice would be comic artist Peter Bagge. He'd certainly cause a lot of debate and letters to the editor even if he doesn't have Hitch's depth and range.
http://reason.com/0202/cr.pb.rock.shtml
http://reason.com/0207/cartoon.pb060702.shtml
http://reason.com/hod/cartoon.pb021502.shtml
Peter