Originally I thought more like 2000, but somehow I see this going the way of 1988 with a likely HRC defeat in 2020...
A lot can happen in four years. On the one hand, four consecutive terms of one party's control of the White House is unprecedented since FDR. On the other, Clinton might prove very effective and popular, and the GOP might do some damned fool thing like nominate Ted Cruz.
After Trump, what becomes of the Republican Party? I can see the TEA Party / Extremist wing wresting control. Ted Cruz was a "true conservative" who had the "moral conviction" to stand up to Trump. I know this sounds absurd, but this is how this wing of the party thinks. If we're going with the 1988 analogy, Bill Clinton won in part because he reinvented the Democratic Party. The GOP will need to run a "new Republican," and the forces that shape that party base are unlikely to allow that to happen. More likely they'll double down.