Obama went big deliberately in 2010 against the advice of Rahm Emanuel. He's been in favor of single payer since 1993 and recently said he would've started with single payer if he redid the law.
He implemented this law because he, fundamentally, wanted to enshrine healthcare as a right. He anticipated the costs issues actually, which is why he fought for a public option. Obama from the start knew that a great law wasn't possible without a transition. Why do you think he brought Big Pharma on board? Expanded Medicaid? He was systematically building constituencies for health care. Obama's never intended the ACA as the final end point.
The name of the game is simple. Get people comfortable with government guaranteeing certain healthcare benefits and access and standards of care. And then do a UHC deal.
The next step is clear to the Left. They will point to the good things the law does and argue for a more liberal model that reins in insurance premium hikes, and enact it.
And 8-12 years. The economic and demographic trends and issues are converging on the next Democratic coalition. Your error is to assume an eternal conservative coalition in this country when one has existed since 1980 and to assume the Reagan era will indefinitely continue for another generation.
Lastly, healthcare is a major economic issue, you do understand, because healthcare costs have outpaced inflation considerably. The Republican Party is inherently unwilling to truly tackle that issue.