I feel like he had the wrong style, he didn’t have the fastest feet and wasn’t a defensive wizard, he was durable and could punch a bit, I feel like Liston would just be able to outjab him and win on points even at that point, you have to make the old man use his legs and chase you and expose the slowing of feet, I don’t feel Bonavena is the man to do that, and if you pressure Liston, that’s not a very good idea, even if he didn’t have the timing to find the big punches, he could still keep him honest with the jab.
I feel that this is fully true for even an early post-Ali Liston likely would've beaten Bonavena, but by the time of the unification tournament? He'd have lost to likely everyone who was at the top of the division.
I think it is possible that Sonny makes it to 1970, although Bonavena or Quarry might beat him at that point in his career, especially if he has a long layoff while following Ali's schedule. He passes away before meeting Frazier.
Liston would be fighting different people and Patterson, Cleveland Williams and Folley probably aren't getting shots especially the first 2. So theres going to be a different group of names for sure. But Liston probably does keep the title until the late 60s when Frazier, Ellis, Bonavena and Quarry come along. If someone takes Listons title before it will not be a 60s Ali opponent. 35 or 36 is the logical time for Liston loses. But Liston looked good in 69 and 70 against Martin and Wepner the Leotis Martin loss was a fluke even then. If he fights Frazier at the right time maybe he can beat him and get him out of the way and keep ruling till Foreman who'll come around when Liston is almost 40. The lack of Patterson, Williams and Folley means the next guys get title shots earlier when its more favorable for Sonny. That is the best case scenario and is more likely not to happen but Liston can certainly stay in the mix until the time of his death in our timeline.
He holds the title for 4 more years, beating Williams III, Chuvalo, Cooper, Patterson III, Terrell. Frazier wins a clear but hard fought decision in 1968, then stops him in the rematch.
The answer in my opinion is not very far. Liston lost his focus about two seconds after the belt went around his waist. He was an accident waiting to happen, and his own personal James Douglas was coming for him. It doesn't matter how much of a badass you are, if you loose your focus at that level, then somebody is going to clean your clock. If you lose half your focus, then somebody is going to clean your clock.
This was sound practice on their part. They had everything to loose and very little to gain. Yes they knew that Liston was dangerous, but there was also the issue that he couldn't get a license to fight in the USA, for two years after he lost the title.
Liston could have reigned until the late 60s or even into 1970 until he gets dethroned by a young, hungry Joe Frazier or Leotis Martin. But this is as long as Liston kept his focus. If he started losing focus and slacking on training, he could slip on a banana peel way before the late 60s or early 70s.