The 38-year-old failed to win a major for the first time since 2016 this season, with Djokovic and Nadal moving up to 16 and 19 titles respectively after splitting the four slams between them, Eurosport reported.
Federer is expecting at least one of them to catch up with him but is still happy to be playing competitively and hopes to be in the mix next year.
"Obviously I would like to keep all my records but it's not realistic," the Swiss said.
"The world of tennis and media asks me about it more and more. There is always a record to beat and to go through. I hope to stay in course for Grand Slams in 2020.
"But being able to play at this level at my age is so nice. And I would like to look at this era like three players who played in amazing way during the same time."