Assuming the GOP pushes through their "repeal now, replace maybe sometime down the road" bill that will be the absolute final death knell for the ACA. Stability and long-term planning (at least longer term than what Congress does) is critically important to insurers. If they don't know the ACA will be in place a year from now and what provisions it will have then, they will drop out at the first opportunity to legally do so. The GOP will kill all the exchanges. Sadly ACA is doing pretty well in my state, I have a lot of gripes about their inflexible paperwork, obtuse procedures and (still) mediocre website, but with a modicum of constructive input from Congress those can easily be fixed.
The GOP is behaving like someone who borrows your car, drives it for days with the oil light on. Eventually instead of a $2 remedy the engine is destroyed and the GOP's response is "I told you this car was a POS."
The time is ripe for both the GOP and the Dems to splinter and a new party arise from the ashes, one dedicated to pursing what actually works and leaving the hot button issues aside.
Single payer would be great, but at this point we will be lucky to hold onto Medicare & Medicaid.