Buffon, a World Cup winner with Italy in 2006, had previously said next season would be his last.
"Yes, I'm 99.9 % sure that's how it will go," said Buffon when asked by Sky Sport if he would keep to an earlier promise to hang up his gloves at the end of the 2017-2018 campaign.
"I will have one final, intense season full of key dates, then it will be time to call it a day."
Buffon, a World Cup winner with Italy in 2006, had previously said next season would be his last, although he is not expected to fully retire until after the 2018 World Cup in Russia -- if Italy qualify.
But the 39-year-old left a tiny chance of going back on his decision, after losing the 2017 Champions League final to Real Madrid (4-1) and the 2015 edition to Barcelona (3-1).
"If we win the Champions League I will continue to play one more season so I can also try to win the World Club Cup and other trophies," he added.