World Rugby has rescheduled the Singapore and Hong Kong tournaments from their usual April slot to October 29-30 and November 5-7 respectively.
More changes may be in the offing as World Rugby will make an update on contingency scheduling early next year.
It is not expected there will be a return to a traditional programme until 2022.
New Zealand headed both the men's and women's rankings after the 2019-20 season was cut short by the pandemic. South Africa was second and Fiji third in the men's section while Australia was second and Canada third in the women's.
South Africa Sevens coach Neil Powell said all teams competing at the Tokyo Olympics will be short of game time as a result of the changes.
"It means that, apart from some regional tournaments, we will probably have one or maybe two official tournaments leading into the Olympics, which is not enough to get momentum for Tokyo," he said.
While understanding the need to put player welfare first, he said it did make planning for next season a challenge.
"We have to laud World Rugby for their efforts in this regard though, as they have offered financial assistance to all teams who qualified for the Olympics, and their efforts with the regional tournaments are commendable," he said.
Some warm-up tournaments have been arranged in Madrid over two weekends in February for both men's and women's sides.
Powell said, "We will have to play in those, no doubt, and we will discuss this as part of our planning for next year with South Africa Rugby.
"The tournaments in Spain will be crucial for us, as will any other regional events leading up to the Olympics and, hopefully, we can play in two or three of those.
"Our main aim for 2021 remains the same, and that is to be successful at the Olympics," he said.
World Rugby is expected to announce another high-performance opportunity for sides early next year.