Indeed, the possibility took a step forward in Monaco, when the German increased his lead over Kimi Raikkonen from just 4 points to 21.
Asked if it worries him that he might soon be only one of two quadruple world champions, French legend Prost said: "I've always told myself -- change the things you can change.
"And don't worry about those over which you have no control. What should I do about it?" he told Germany's Welt newspaper.
"He will probably surpass me one day.
"When I lost my record for the most grand prix wins to Michael Schumacher, that was something else," the 58-year-old admitted.
"I was not happy about it. If you're at the top, you want to stay there.
"But now, if I am the second, third or fourth most successful driver in formula one history, nothing changes," added Prost.
Prost admitted he rates Vettel highly, and doesn't detect any "serious" weaknesses in the 25-year-old Red Bull driver.
"In recent years, it was always said that he can only win races from the front," he said. "Well, he has refuted that in the past season.
"I spoke with him last summer, when Fernando Alonso was far in front of him. I said 'Can you do it?' and he answered 'Yes, clearly'.
"It takes this sort of conviction to be a great driver," added Prost.
He admitted, however, that Vettel's bad relationship with teammate Mark Webber could spoil the momentum.
Prost is famous for his toxic rivalry with Ayrton Senna, and admitted: "That can happen, yes. I lost the title in 1990 because of Nigel Mansell.
"It can happen very quickly."
It is for that reason that Red Bull is reportedly considering pairing Vettel with his friend Kimi Raikkonen next year.
Prost insisted: "But when you are fighting for the title with his teammate, is he your friend? My experience is quite the opposite."
Prost also commented on the controversial tyre situation in F1, where Pirelli is expected to supply slightly altered rear tyres in Canada next time out.
"There are three possibilities," he said. "First, there is a safety problem, then this decision is absolutely correct.
"Secondly, in future there will be two or three pitstops instead of four, which I also think would be good because the races have become very confusing.
"But third, if it (the changes) is due to the influence of external forces, that would be a disaster," said Prost.
"I don't know which is true, but two of the three alternatives are positive, so I think that's a passable statistic," he laughed.
More seriously, however, Prost was asked if it is not fair that the changes might positively affect Mercedes and Red Bull, and hurt Lotus and Ferrari.
"I know," he answered. "But I believe that this change will not change so much. Lotus and Ferrari will not lose the advantage that they have."