The next step is to offer a government run health insurance option that is available to everyone (not just the poor and old).
I think people get a little too hung up on the public option. Would it
really matter whether everyone was covered by a government-operated pool, or by a single non-profit health insurer, or even a single for-profit health insurer that operated under heavy government supervision? It matters if people are covered by a mix of the above, but only because that means we have a bunch of people in separate pools.
The reason for pooling everybody into a single risk pool is to exploit monopsony power and drive down the cost of care by telling doctors and providers that if they don't provide at such-and-such a rate, there's nobody else to provide to. At that point I don't really see how it matters who administrates the pool; it's one of those "waste" issues, maybe, but the quality of care will be determined by what rates the risk-pool is allowed to offer.