If Lieberman didn't switch after endorsing McCain and giving the keynote at the 2008 RNC, I don't see Manchin jumping ship either.
Well at least Connecticut Democrats were smart enough to dump Lieberman. West Virginia Democrats primaried a long term member of Congress with Mike Oliverio, who might even be worse than Manchin, so I wouldn't expect too much from them.
Can you imagine the Republican party doing the equivalent? Like having Maine Republicans primary Olympia Snowe and replace her with Jacob Javitts? Hahaha, of course not.