If they go through with Space Force (and why not, since Russia and China have similar entities), there's a strong possibility it will be under the aegis of the already existing USAF Space Command, maybe reorganized with the aerospace operations of the Army and, to a greater degree, Navy. Some civilian space programs will probably get tucked under there too.
Point being, USAF already has physicians who specialize in aerospace medicine, and if they get a Space Force (or more probably Space Corps), then you will have an opportunity after you become an Air Force doctor.
But a USAF doc attached to space command...that's what Dr. Bellows in "I Dream of Jeanie" was. Is that who you wanna be? A really Freudian weirdo who hasn't noticed that your subject's girlfriend is magic, after how many seasons, even spanning the leap from black-and-white to color TV? 😉