Warning: This blog is uninformed beyond what a reasonably intelligent person can gather from reading news on the web
Even if the next President is a Democrat elected by a landslide - let's say 342-196 in the Electoral College, it's unlikely in the extreme that Congress will flip. A few seats here and there, and maybe the Senate goes Democratic by a razor-thin margin.
So the main thing to expect of the Presidential term from 2017 to 2021 is some really really important Supreme Court nominations. Some of the more liberal side of the court might just be hanging on until they know they will have a reliable, rational replacement. Who knows, something could even happen to one or two of the "conservative" justices.* For women's rights, LGBTQ rights, and... well... to keep the terrified rabble howling for a fascist theocracy at bay, the next President must be a Democrat. I don't even mind if it's Clinton, although I would much prefer Sanders.
* - A quote from Clarence Darrow's The Story of My Life (1932): "I have never killed any one, but I have read some obituary notices with great satisfaction."
Let's just say, in a few select cases, I look forward to that opportunity.