Haye was defeated by Wladimir Klitschko in July and has said that he is considering hanging up his gloves.
However, the Brit added that he would only enter the ring one last time to fight Wladimir's older brother Vitali.
"He's still young, he's not had too many hard fights," said Khan. "He can definitely win a world title again and finish up with a win. You never want to finish with a loss. I'm sure David probably will have one more fight [and] win that.
"Financially I'm sure he's secure - he's made a lot of money in boxing. There's always that doubt in the mind when you walk out of a sport losing."
Khan will next fight Lamont Peterson in December in what is widely thought to be his last bout before moving up a division.