It's also not completely implausible that Manchin could lead the WV legislative Democrats back into majorities (though the House got pretty heavily Republican in 2014).
The same way that Governor Steve Beshear took back the Kentucky Senate for Democrats? Or how Gov. Jay Nixon took back the Missouri legislature?
Face it, West Virginia is gone. He may be able to hold back the tide a little by keeping the governor's mansion in Democratic hands, but after he leaves office, watch the WV GOP consolidate its gains at every level in the state.
Democrats managed to regain the MS state senate in 2007 before losing it again (probably for good this time). I don't think it's implausible WV Dems could get one last hurrah before partisan gravity sinks them for good.
but Haley Barbour was Governor. Generally, when one party leads, the other party gains, so I think West Virginia Democrat losses get worse if Joe Manchin is Governor.