I'd say the odds are good. A Constitutional ruling would, as the article points out, make the "ACA" null & void overnight. Millions will lose coverage instantly, both because of subsidy loss or loss of government funded plans. If the GOP steps in right away with a plan to SAVE the ACA, they will have lost my vote, and many others, regardless of who they put up. I would also question the viability of the GOP offering up a subsidy plan, as I don't know that it can be implemented quickly enough to save the system. The answer? Well, single payer, of course. FedGov just takes over the healthcare industry. Insurance companies will, mostly, be destroyed overnight. Those that aren't become instant contractors for the FedGov, essentially making them federal employees.
Here's the question...
If, as you say, ACA becomes null and void, then there is no law for McConnell to add four words to to fix. He has to start from scratch with a new law. Is that going to be the likely interpretation? I doubt it. McConnell will say that rest of the law is valid and they will fix it.
However, another thing that is not in the law is severability. Congress purposely took out the severability law, just like with federal exchange subsidies. Is SCOTUS going to act as if severability were still there anyway? Will McConnell? Will lack of severability cause SCOTUS to toss out the whole law?
I think that one of the reasons that Roberts twisted himself like that was because of the lack of severability.
-PJ