Change my view: physician compensation will inevitably decrease

In the U.S., insurance companies essentially have unilateral control over physician compensation (for anything other than cosmetic/elective stuff). In recent years, we have seen declining insurance reimbursements to physicians. We are not yet seeing decline in overall physician salaries because physicians are working longer hours and seeing more patients. This is only possible because physician supply is tightly controlled like a cartel. I see two possible scenarios for the future:

1. insurance companies maintain power or continue to gain power with corporatist reforms like Obamacare, or
2. we get single-payer or medicare for all, in which case insurance companies will be replaced by an even more powerful entity.

In both of these scenarios I see reimbursements to physicians continue to decrease. The only bargaining chip physicians have is control of physician supply so physicians can take heavier workloads to maintain overall salaries. But that cannot be sustained forever – there is only a finite number of hours/week physicians can/will work. So eventually after medicine becomes a living hell for physicians with 7day 100hr work weeks and physicians can't take being rear-ended any further, the ACGME will be forced to open up residency spots, physician supply will increase, and thus physician salaries will inevitably decrease. But I'm just a premed so what do I know? Change my view.