No one agrees on the exact numbers, but it's a safe bet to say that over the next few years millions of Americans will sign up for health insurance on the now-open public exchanges.

Some of those people will have been shifted to the exchanges by mostly smaller employers. But larger employers aren't likely to be part of that wave. In fact, industry analysts say most Americans will continue to get coverage through an employer.

That's according to a survey of 532 small businesses designed to elicit their attitudes toward health coverage. Sponsored by small business insurer Employers Holdings Inc., the survey found that two in five small businesses with between one and 250 employees already offer coverage, and another one in five intends to do so within the next three years.Moreover, even though many small businesses aren't under any obligation to provide health care coverage to employees, nearly two-thirds may do just that in coming years.