Anyone who thinks their specialty is immune to mid-level encroachment is smoking the crackpipe. I'd encourage you to read the Anes forums, circa 2005/2006, where some thought the CRNA thing was just a 'fad' and would go away.
The medical industrial complex---and make no mistake about it, health care is an industry, subject to all of the same economic pressures as any other industry---loves the PA/NP. They can throw them into in any context (outpatient, inpatient, adults, peds, etc), with minimal training, and they can do much of the scutwork (or what we physicians perceive to be scutwork).
They view us physicians as a total PITA: we take too long to educate and train (sometimes true: do I really need a sleep physician, PGY7+, to tell me someone's too fat to breath well at night?), we're expensive (to pay, to insure), and we're high maintenance. In any other industry, the economic mechanisms at hand will find a way to circumvent such a PITA commodity, and that's exactly what's happening in medicine.
So what do we do about it? We'll probably do nothing. We're not organized, and we don't care all that much (as individuals). Most of us have good jobs now, our immediate livelihood is not threatened. I can't say that about the generation following us.
What would I like to see happen?
-- Reduce the # of years in education/training (we've had this discussion before), so we can get physicians into the workforce sooner.
-- Stop making a fellowship/BC out of everything (again, too much formal training): more on-the-job training and certifications
-- get rid of BC, it's an unnecessary credential (test the individual all you want while they're in training, including a mandatory exit exam, but once they've graduated, they're done, and should be allowed to practice!)