Full details are expected by the end of January, with the men's Six Nations set to start as planned in February.
Ireland, Scotland and Italy's Women's Six Nations fixtures may double as 2021 World Cup qualification matches given none of the three have yet secured a place at the tournament.
The Under-20 Six Nations has also been delayed until later in 2021.
Like the women's tournament, it would normally run at the same time as the men's Six Nations.
The news comes after the Rugby Football Union told BBC Sport last week it had "concerns" about the tournament because of complications around planning. England are the competition's only fully professional side.
Organisers say they are "fiercely committed to the promotion and development of rugby at all levels, particularly the women's game, where we see exciting opportunity for growth".
With the men's Six Nations set to go ahead on its original dates, despite concerns around French participation, it would give the women's tournament an opportunity to step out of the men's shadow.
The World Cup starts in New Zealand on 18 September and there are still three places to be filled, with 12 countries in contention to secure them.
There are six European countries trying to win places, with Spain, Russia and the Netherlands still needing to complete the 2020 Rugby Europe Championship.
The winner of this will join Italy, Ireland and Scotland in a European qualification tournament that was originally scheduled to take place in December 2020, but was postponed amid coronavirus concerns. The winner will get a place at the World Cup in Pool B, while the runner-up will have one last chance to qualify through the repechage.