I think this analysis makes sense from a business viewpoint, but I'm not sure it holds up from a medical standpoint. Please to explain...
I think you're undervaluing radiology's role in the day-to-day business of modern healthcare delivery in the U.S. It seems like your analysis assumes that the general, patient-facing specialties are capable of providing cheaper, more efficient care if only they wouldn't order so many imaging studies. They won't do that though, because they can't. To oversimplify it - they don't know how. You might as well try to tell a surgeon to start operating without anesthesia. We have entire generations of providers who have been trained to practice based upon the radiologist's input. And, as mid-levels expand the scope of their practice, there will be more and more providers with a greater reliance of imaging.
The second issue, which isn't really that unrelated, is one of standard of care. Let's assume, for a moment, that providers are willing to forego the stat head CT for every presentation of new-onset headache (unlikely, as explained above). What about the patients? The public has become accustomed to a very high standard of care in this country, and - for better or for worse - radiology is a pillar of that care. For one, medical imaging offers a substantial CYA component to providers, and two, pictures offer a psychological reassurance to which the patient can relate. I don't see how an appreciable decrease in imaging utilization can't also be accompanied by a sea change in medical litigation that fundamentally changes our country's concept of standard of care. It's possible, but it's a huge hurdle and a change that I think is unlikely.
Overall, my point is that there are more than just dollars and cents factors that affect radiology's viability.
And in case anyone is thinking, "well, the specialists will just read their own studies", I think that's been covered sufficiently elsewhere in the forum.
I'm not trying to purport that radiology won't undergo changes, I just don't think those changes will fundamentally alter the specialty's place in medicine. Salaries will go down, but not because there will be a huge change in how or with what frequency medical imaging is used. Salaries will go down because costs must come down, and imaging is an obvious place to start because of its scope and scale. But that sort of change has a floor. As opposed to what I think bronx is proposing, which would represent a basal change that would affect the overall utilization of medical imaging.