Carlos Sainz is ready to replace Sebastian Vettel at Ferrari and Daniel Ricciardo must replace the Spaniard at McLaren.
Negotiations to seal the two moves are underway and no final agreement has been reached, but are expected to be completed and announced this week.
McLaren has been chasing Ricciardo for some time and his signature is a scam.
But they must release Sainz from his contractual obligations before signing the Australian.
Sainz was in talks to remain at McLaren after 2020, but the call to join a top team convinced him to move.
The teams and drivers have been in negotiations for some time and the conversations are understood to be in their final stages.
The domino effect on the driver market was triggered when negotiations on a new contract between Ferrari and Vettel failed.
Ferrari announced on Tuesday that the four-time German world champion would leave the team at the end of the 2020 season, which is currently on the ice as a result of the coronavirus crisis.
Ferrari identified Sainz as the ideal support driver for Charles Leclerc, whose starring performances in his first season with the team last year damaged Vettel's status and precipitated his departure when he was not prepared to accept reduced contract terms.
Ferrari will face Sainz in the kind of reserve role that Valtteri Bottas plays for Lewis Hamilton at Mercedes – fast enough to be close to him and fight a battle with other leaders, but not with the team leader.
Sainz, who previously drove for Toro Rosso and Renault before moving to McLaren last year, is likely to see the move as an opportunity to prove himself as a first-rate driver.
He stood out in his first season with McLaren last year and his strong racing performance earned him the Ferrari call-up.
What about Ricciardo?
The signing of Ricciardo is a big boost for McLaren, which last year made impressive progress back to fourth place in the championship, after a few dark years falling on the grid.
The Australian came close to joining them in 2019 when he left Red Bull, but in the end chose Renault because it was more competitive at the time.
But the fortunes of the two teams diverged last year, with McLaren climbing the grid and Renault's progress back to the top; in fact, they were behind McLaren to finish fifth in the championship.
Ricciardo has now decided that McLaren is a better bet for the future – a decision partially influenced by the switch to Mercedes engines in the 2021 season.
This is one of several important decisions made by the new team leader, Andreas Seidl, who has impressed with his meaningless approach since joining the team in May last year.
Who will replace Ricciardo?
Ricciardo's departure leaves a space at Renault alongside Frenchman Esteban Ocon, assuming the automaker will stay in F1 next year.
Renault is said to want to promote one of its young drivers to the position, but Vettel and two-time world champion Fernando Alonso were mentioned as possible candidates.
Alonso said at the end of last year that he would consider a return to F1 after two years, but will have to consider whether he believes Renault will give him the competitive car he says he wants.
But he has fond memories of the team, having won his two world titles with them in 2005-6. He also returned there for a two-year period in 2008-9, after his move to McLaren went sour in a tumultuous year alongside Lewis Hamilton in 2007 and before moving to Ferrari.
He said he sees the new regulations being planned for F1 as a chance for the field to be more competitive.
But these have now been postponed for a year until 2022, as part of a package of changes to reduce costs due to the drop in revenue from the truncated 2020 season.
This means that Alonso – who will turn 39 in July – would need to be prepared for a 2021 season, probably in the upper midfield, and it remains to be seen whether he wants to go through it again after five years in a non-competitive McLaren between 2015 and 18.