Why not eliminate this anachronistic charade of the general practitioner and use nurse practitioners and physician assistants to fill the gap? This is already happening in rural areas, which sometimes lack even a single primary care physician.
Private practices will not disappear, but increasingly they will become a niche to provide good old fashioned service to the generation in the habit of "going to see my doctor," while the more mobile young have already discovered the instant gratification of clinics and particularly the ERs.
Why, exactly, would a medical student choose to pursue a career in primary care? And why would they choose not to?