Seriously, for a moment, let's just indulge in the idea that Hillary was President (you know, the spouse of the former President that floated universal healthcare). Do you really think that Hillary would let the ACA either fall apart due to neglect
If Hillary Clinton was the US President right now, the health insurance market would not look materially different because the Republicans haven't changed much yet, and what changes they have promised haven't gone into effect.
But I can wager that she would be trying desperately to fix some of the identified flaws with the ACA, and Republicans would be stonewalling her all the way. They would be wailing about death panels and the end of America at the top of their lungs, and simultaneously refusing to do anything about it. Remember the Party of No? Republicans would force the US to live with the ACA exactly as it currently exists, warts and all, for as long as possible.
But what's the end game in that? I mean EVENTUALLY they were going to get a Republican majority, so holding the ACA in current form would just delay their current problem until that later time, and it's not like they haven't had six years to figure this shit out. Why would they want that problem later instead of now?
No, I think I agree with EV2020 and that they are absolutely committed to repeal at this point, consequences be damned. They'd rather throw 20 million Americans off of their current insurance, and try to spin it as "it's for your own good" than conceded that the Democrats actually helped people. They'll throw in some tax breaks for their wealthiest constituents to try to save face for fucking with the poor, like they always do. Maybe their replacement plan will actually be better for some folks, probably rich self-employed business owners or other high-income folks without employer insurance, but I don't see how it could possibly be anything but worse for everyone else.
Well scratch that, I do see one way. They can always just deficit spend the bejeezus out of it. They could wholly repeal the ACA and then give every American family a $15,000 refundable tax credit for health insurance. It would crash the federal budget, but it would technically deliver on their promises of potentially better coverage, with more choices, at lower cost to Americans.