In truth, the American system of health care — in which most people get their private health insurance through their employer — has always been rather odd. Why should quitting a job also mean you have to get a new health insurance plan? Why should your boss get to decide what options you have and negotiate the cost of them? Employers don’t get to select our auto insurance or mortgage company, so why should health insurance be any different?

If there is uncertainty around how the employer-provided health insurance system will evolve, there is even more around who will ultimately pay the bill. It could be the federal government, via insurance subsidies, or individuals who must pay for more of their health care. In a perfect world, lower costs would come from a more efficient system that provides better care at lower costs. But no one knows what the actual system of, say, 2025 will look like, any more than people could have foreseen the decline of pensions when the 401(k) option was added to the tax code.

Michael G. Thompson, managing director at S&P Capital IQ, argues that the parallel with defined-benefit pension plans is an apt one. For decades, those plans were a major benefit offered by large employers. But as other options became available that allowed employers to more cheaply provide retirement benefits with fewer administrative headaches, which 401(k)s provided, employers shifted to 401(k)s en masse.

“We still expect some companies to hold on to their health care plans, just as some private companies still have pensions,” Mr. Thompson said. “But we think that the tax incentives for employer-driven insurance are not enough to offset the incentives for companies to transition people over to exchanges and have them be more autonomous around management of their own health care.”

The advantages are particularly clear for companies with lower-paid workers, who may be eligible for federal subsidies under the Affordable Care Act aimed at those employees making up to 400 percent of the poverty line.

Not everyone is so sure. Employers may not love the administrative challenges of administering a health plan, but they have been offering these plans voluntarily for decades, because employees value the perk. An employer who backs away from offering a health insurance plan directly, instead sending workers to the exchanges, may lose a competitive advantage in hiring. (Yet companies’ experience with substituting 401(k)s for pensions may have taught them that employees had little choice in the transition, and just accepted it.)

There is another strong reason that employers might not rush for the exits. When an employer subsidizes a worker’s health insurance plan directly, the subsidy is tax free to the employee. So the employer is effectively getting more bang for the buck in its total compensation. If an employer gives its workers extra pay to help them buy health insurance on an exchange, that money is taxable income.