"To actually go to Rio and win again would be a feat in itself," said Bolt, speaking ahead of the Weltklasse Diamond League meeting in Zurich.
The Jamaican will run in the 100 meters after a world championship sweep of the sprints in Moscow, where he talked of working hard to attain "the greatness thing."
Most would say he's achieved that already. He completed the same triple at the Olympic Games in Beijing and London.
"For me, the key thing is just to go to defend my titles, and that's my focus. It would be the first time anybody has ever won three times in a row," Bolt said.
Bolt became the most decorated athlete in world championships history this month, with his career tally of eight golds and two silvers lifting him above American great Carl Lewis.
Three more golds for Bolt in Rio would still leave him trailing Lewis' Olympic track and field record of nine golds and one silver.
"I won't be adding a fourth event in Rio, for sure," said the 27-year-old Bolt, whose 34th birthday could fall during the 2020 Summer Games.
Bolt's news conference was held at FIFA headquarters, across the city from the stadium where he will run today. Bolt was greeted on arrival by FIFA President Sepp Blatter, and later accepted a blue FIFA football shirt bearing his name and the No. 9.
Blatter joked that nine seconds was probably the limit for Bolt, whose 100 world record set in 2009 stands at 9.58. Bolt suggested he was capable of running in the 9.70s at Weltklasse, where a warm, still evening is forecast.
"I have gotten a lot of rest," said Bolt, who last year in cool, wet conditions set a Weltklasse meet record of 19.66 in the 200.