It will definitely happen.
Heck, in Minneapolis we're already seeing it within the Democratic party. You've got traditional Democrats, and then you have Democratic Socialists of America, who are already going out and challenging traditional Democrats as well as Republicans, and making some headway in what is a pretty liberal environment.
You guys can sit here and say "no, no, no" all you want. I don't care. It's happened every other place on the planet where the human species resides, so it's going to happen here. In fact, it has happened here. It's just that the political apparatus in place has, generally speaking, been able to suppress the fracturing of parties. But as differences become more entrenched in what we've known as the major parties, those suppression efforts will slowly fade.