Numbers don't lie. PPACA is a bad deal for younger healthier people. It doesn't reflect their expected value or risk. It's mispriced. They will, all else equal, continue to avoid enrolling in the expected or promised numbers. That's not going to change. The other thing which isn't going to change is that some of the very people who for the past seven years ran around spitting at ObamaCare, waving "Obama is a monkey" signs and voting for people who swore blood oaths to rip up the PPACA root and branch, turned out to have a different feeling about ObamaCare when Uncle Bud was covered for the cancer meds he needed or Cousin Sherri finally got enrolled in a program to help with opioid addiction. There are relatively few people who will, if push comes to shove, place their ideology over their survival. They won't brag about this. It's not the stuff of heroic stories. But it is human nature. And even a lot of big bad Republicans who wanted to kill Obamacare still flinched away from taking away popular benefits.
Now that there is Republican control of the executive branch with all of the awesome discretionary prerogatives of that come with it, Trump and his minions could accidentally on purpose help along ObamaCare to an early grave. And there wouldn't be too much that Democrats could do about it. Or given Trump's desperate need for acclamation, he could attempt to reshape the PPACA via executive fiat and administrative choice into something that keeps coverage for many voters but slows skyrocketing premium and deductible growth. I don't think this will work even if Trump were a detail oriented policy wonk, which he is most assuredly not. So the most likely scenario is that the PPACA continues to limp along until the next midterms and then the one after that and so on. It's never going to be unpopular enough to kill. But it will never be popular enough to fix either.
