I think there will definitely be a squeeze, be it through higher supervision ratios, less pay, whatever, but long term I don't see these corporate groups surviving because they're based on ripping off private insurers who have way more power. The massive hospital systems, which are not particularly financially sound either, will probably be the next to employ all doctors so they can bundle bills and keep the fees from us, surgeons, radiologists, etc.
Somewhere down the line it may be the federal government itself employing us - at our place it feels like each year less and less people have private health insurance and I don't see that trend reversing.