No.
Khabib mauls him.
Fighting is a skill. No skill, no chance.
Once you are good at the skill however size comes into play.
BTW why do you assume he would beat him even now, after 8 years of training?
Khabib would definitely NOT spend even one second in striking distance. He would tie up and hold on for his life.
He has the better cardio and years ahead in the skills department.
My opinion, street fight (only way this would ever happen), 50-50%.
One knockout punch for FN or Khabib clinches, chain-wresrling, Francis gases, Khabib gets too position and punches him until the fight is broken up.