I don't really disagree with this, and in fact it sounds optimistic to me, provided you're asserting that a new party will be born from the broken duopoly that your prediction will cause. Which you may not be. I'm not trying to put words in your mouth.

Edit: On second thought, I do somewhat disagree, as watching the democratic party flirt with and ultimately push back against a Candidate Sanders in 2016 definitely seems like a deviation from the plot-line you've presented. I can envision a future in which the Dem party is captured by further left factions as young people grow up and become more and more engaged with electoralism.