Dude, chill.
Your insinuation is that pain patients are not ever satisfied? Really.
Sometimes, in medicine, especially with people without much experience, there is a tendency to equate cynicism with wisdom.
It's true that you need to remain vigilant for people trying to take advantage of you, but most patient's I've seen in pain clinic, Ortho clinic, Sports Medicine clinic, Outpatient MSK clinic get significant pain relief for months before they need to return.
And as far as I know, no one is saying that you'll only get paid if you cure someone of pain forever. I think (just guessing, admittedly) that chronic pain will be classified as a chronic condition. I'm not sure what the metrics for quality or success of treatment will be after the end of fee-for-service, but most things are quantifiable if you give it a try. Maybe it will be number of months of pain relief, or a functional capacity scale where pain per se is not what is measured, but the ability of patients to perform whatever task the pain was preventing them from performing.
Also, there will always be a cash market for injections and Botox and PRP, etc.
So, again, not sure what exactly things will look like, but my guess is that it won't be the end of the world, that kinks will be worked out over time, and that we'll adapt.