Maxine Udall talks about the morality and microeconomics of heath care. Yes, some physicians accustomed to their privileges might leave the profession before health care reform becomes a reality. It's a free country: for every one who leaves there are a hundred who would happily take his place, either as physicians (once we remove the artificial limitations and rent-seeking from medical schools*) or as substitutes such as nurses or physicians assistants who can effectively treat many conditions.
*Not all strictures imposed by medical schools are artificial and pragmatically unjustified. But some clearly are, and serve only to artificially restrict the supply of physicians.
Everyone talks about the iron laws of economics until it's their professional privilege that's on the chopping block. I know whereof I speak: my own middle-class privilege was completely destroyed by economics. When I was young, it happened that I had real talent at computer programming. Then, the demand for people who could just turn the damn things on and make them do something far exceeded the supply, and those of us with demonstrated competence could make quite a bit of money. What we didn't do was artificially restrict the supply; by the time we clued ourselves in to how the capitalist system actually operates and started creating expensive and arbitrarily limited credentialing mechanisms, it was far too late: the invisible hand corrected the imbalance between supply and demand and for all but the most prestigious few, programming became a working class profession with working class wages. (And working class wages today ain't squat.)