Remember this is a single statistic about a huge, multifactorial outcome. A couple things to consider: all physicians are not equal. It's likely that new Caribbean grads will get edged out before anything happens to US MDs and DOs. Also consider that there will be a generation of retiring physicians (boomers), leaving a gap for new grads to fill. Boomer PAs and NPs are far less common. The statistic doesn't show that the 3% is subtracting retiring physicians and adding new grads. The corresponding stats for PAs and NPs are larger because there will be far more new grads than retiring boomers.
Also legislation around PAs and NPs is evolving. I predict their scope will expand until patients start getting hurt, then they'll need to start worrying about lawsuits and their employers won't want the liability. Thus a PA or NP degree is riskier, in my opinion, because their scope of practice and pay is still being established.
Finally the physician lobby is extremely interested in and extremely adept at preserving its own wealth. For better or worse, we hold the most wealth out of the healthcare professions and that translates to political might.
I wouldn't worry too much about this for now though I agree it's something to be aware of.