Medicare Expansion + Private Healthcare = ?

If Medicare is expanded as a public option for all, while private health insurance is also maintained, what will the result be?

If more people choose Medicare instead of private healthcare, the insurance industry could lose revenue.

On the other hand, if Medicare pays costs that are set by private insurers, that would raise costs for both private insurers and taxpayers.

Eliminating private health insurance would never make it through due to resistance, so why bother even analyzing that prospect?

What changes to regulations have Democrats proposed that would lower costs of care, costs of education for people seeking medical/dental training, lower pharmaceutical costs, or lower any other costs?

All Democrats want to do is protect and/or drive existing prices higher by subsidizing them with taxes on corporations and the rich.

Why aren't there any Democrats who propose health care solutions that don't stimulate more inflation by subsidizing already-overpriced health services and products?