Mixed feelings for me about Sainz to Williams.
On one hand I think Williams under Vowles has a better current trajectory than Sauber/Audi or Alpine have, the latter two seem to be having issues on the management side. Audi might well pour a lot of money into the team and develop them, but that's a few years away probably.
On the other hand I wanted Sainz to go to Mercedes for at least a year. A Russell/Sainz pairing would have been a pretty solid team, with two drivers who are good at thinking on their feet, especially about strategy and track conditions.
That leaves, one Sauber seat, one Alpine seat still? And perpaps a VCARB seat if Riccardo moves to Red Bull? Feel like I have missed one somewhere.