Two problems with that. A) there is no reason to believe that Roberts would do that, and B) Brownback's got his own problems and is no shoe-in for re-election.
Oh well in that case the smart thing to do is elect the Pro-choice, Pro-amnesty, Pro-Obamacare guy.
What does that do with the overly-optimistic idea that Roberts could retire in a year and allow Brownback to appoint his successor?