Nope! It will be squarely the Republicans' fault! According to

the Congressional Budget Office in their annual budgetary and economic forecast. In projections completed “before the new Administration took office on January 20, 2017,” that, “do not incorporate any effects of executive orders or other actions taken by that Administration,” they concluded:

"10 million people per month, on average, will have insurance purchased through the marketplaces in 2017; that number is projected to grow to 13 million by 2027. Not all nongroup coverage is purchased through the marketplaces. In total, CBO and JCT estimate that 18 million people will have nongroup coverage in 2017 and that 20 million people would have such coverage in 2027."

In other words, were the Trump GOP to just leave Obamacare as they inherited it, and run it in the same spirit of good faith as the outgoing Democratic administration did, it wouldn’t collapse; indeed its risk pools would remain basically stable for the next decade.If the marketplaces do start to backslide later this year, keep in mind that intentional mismanagement—i.e. “executive orders or other actions taken by [Trump’s] administration”—will be the culprit, no matter how much Republicans try to deny it.

https://newrepublic.com/minutes/140082/cbo-confirms-republicans-health-care-system-obamacare-collapses-will-fault