For WV it's whenever one of the senators retires and Moore takes a run.
Even if one of the incumbents retires at some point, Capito wouldn't be favourite to win, unless the Democrats picked a bad candidate to run against her (say, Ken Hechler... if he's still alive by then). She wouldn't be a terrible candidate statewide, but she wouldn't be a good one either (she's actually quite vulnerable to attacks on her socially liberal, for West Virgina anyway, views, and, unlike someone like Rockefeller, she's nowhere near left-wing enough on anything else to easily deflect such attacks). She's an excellent candidate for her district o/c, but that's not the same thing at all.
