My father was recently diagnosed with the early stages of emphysema, if he quit smoking would it progress?

Possibly: Quitting smoking can definitely slow down the progression of emphysema. If your father continues to smoke, his emphysema will definitely worsen.

Just quit: If your father quits smoking, the emphysema won't get worse. But, i can't guarantee that his lung function won't continue to decline. Still, quitting is the only way your father can prevent further lung damage. And with lung damage, once it's gone, it's gone.