Delegations from both Los Angeles and Paris met the IOC in the Swiss city on Monday and Tuesday.
The committee agreed by consensus to award the 2024 and 2028 Games at the same time, effectively guaranteeing that Paris and Los Angeles will be the hosts although it is not clear which year each city will get.
IOC chief Thomas Bach, who lobbied for the groundbreaking move, had said that, if his plan was agreed, formal discussions would begin with both camps on which city goes first.
French President Emmanuel Macron, who flew to Lausanne with Paris Mayor Anne Hidalgo, has repeatedly said France was only competing for 2024.
"After three failed bids we don't want to lose a fourth one," Macron told reporters following the Paris pitch. "I am here to convey a message to say our people are ready to host these Games."
Support ... and some opposition
But, although a recent poll showed around 60 percent of French people in favour, not everyone wants the games to come to Paris either in 2024 or 2028.
An oped signed by experts and researchers in Tuesday's Libération newspaper called on Paris to drop its bid.
The signatories argue that the Olympics Games are too expensive and bad for the environnement and the local population.
"As was the case in Brazil two years ago, it creates environmental disruption, they're very expensive so taxpayers have to foot the bill and only a small fringe of people benefit from it," Pierre Guerlain, a professor at Nanterre Univeristy who signed the appeal, told RFI. "In France, the new installations, which will be very expensive, will be of no use to ordinary people afterwards. Also, it's always more expensive than planned."
The economic impact of the games are often talked about. The common consensus is that it is mostly negative for cities organising summer games.
"Generally, cities and countries that host the games, have ended doing rather badly at the end of it in economic terms," says David Forrest, a sports economist at Liverpool University. "They've tended to experience a fall in the long-term growth rate. It's also been found that tourism over the years will actually suffer as a result of hosting the games."
Paris promises cheap, eco-friendly Games
The French authorities have been trying to reassure the public.
Hidalgo has promised that the games will be cheap and environmentally friendly. Only a small number of new venues will be built in and around Paris, while the budget should stand at around six billion euros.
"Actually it could be different this time," says Forrest. "What's different this time is that there are no other bidders. The last city that did well out of hosting the Olympics was Los Angeles itself in 1988. Then it was the only bidder and it didn't feel it had to build lavish venues and was able to go for modest games. They even made money out of it."
The IOC seems keen to make the Games as cheap as possible in the hopes of not seeing multi-million dollar facilities left to crumble and rot. The economic cost of the games actually discouraged cities from bidding, with Rome or Budapest withdrawing their candidacy last year.
Which is maybe why Bach talked about a "win-win-win" result when talking about the 2024 bidding process.