Re: Muhammad Ali's career if never drafted?
As Pepe said, there was talk of Ali facing Bonavena and Spencer next, as well as a rematch with Patterson (due to his back injury in the first fight).
In 1968, you might have seen Ali defend against guys like Ellis, Peralta and Leotis Martin while Quarry and Frazier were being built up as contenders. I think Ali defends against Foster and Quarry in 1969, and then faces Frazier about a year sooner than he did in real life.
You never know...Maybe Ali suffers an injury and his career ends entirely. But assuming he stays healthy, these are guys that he may well have faced during those three years.