Updated following official confirmation that Vinales will leave Yamaha at the end of 2021...

Factory Teams

Repsol Honda:
Marc Marquez (End of 2024)
Pol Espargaro (End of 2022)

Monster Yamaha:
Maverick Vinales (End of 2021)
Fabio Quartararo (End of 2022)

At Vinales' request, Yamaha has released the Spaniard from the second year (2022) of his current contract. Potential candiates to take over his seat include Morbidelli, Dovizioso, Gerloff, Fernandez...

Lenovo Ducati:
Jack Miller (End of 2022)
Francesco Bagnaia (End of 2022)

Suzuki:
Alex Rins (End of 2022)
Joan Mir (End of 2022)

Aprilia:
Aleix Espargaro (End of 2022)
Lorenzo Savadori (End of 2021)

The only Factory team seat still available is alongside Espargaro. Vinales is now the hot favourite, while Aprilia had previously been hoping to convince Andrea Dovizioso to return

Red Bull KTM:
Miguel Oliveira (End of 2022)
Brad Binder (End of 2024)

Independent Teams

Gresini Ducati:
Fabio di Giannantonio (End of 2022)*
Enea Bastianini (End of 2022)

Petronas Yamaha Sepang Team:
Franco Morbidelli (End of 2022)
Valentino Rossi (Yamaha contract, end of 2021)

The Malaysian team is yet to officially renew with Yamaha, but a new deal is now back on track after competition from VR46 for the M1 supply. Morbidelli has a contract with the Sepang squad for 2022, but might he now move to the factory team in place of Vinales? Rossi says he will decide on his racing future during the summer break meaning Petronas may even need two new riders in 2022. As with the Official team, Dovizioso, Gerloff and Fernandez plus Petronas Moto2 riders Vierge and Dixon have all been linked to the satellite M1 seats.

Tech3 KTM:
Remy Gardner (KTM contract, end of 2022)*
Danilo Petrucci (KTM contract, end of 2021)
Iker Lecuona (KTM contract, end of 2021)

Petrucci, Lecuona or Moto2 star Raul Fernandez expected to get the remaining 2022 Tech3 seat.

LCR Honda:
Alex Marquez (HRC contract, end of 2022)
Takaaki Nakagami (HRC contract, end of 2021 'and beyond')

Pramac Ducati:
Johann Zarco (Ducati contract, end of 2022)
Jorge Martin (Ducati contract, end of 2022)

Aramco VR46 Ducati:
Luca Marini (TBC)
?

Valentino Rossi's team gets its own grid places for 2022, effectively taking over the Avintia Ducati spots. VR46 will use Ducati machinery, with current rider Luca Marini (run in partnership with Avintia for his rookie season) on one of the bikes. The second seat could go to the likes of VR46 Moto2 star Marco Bezzecchi... assuming Rossi (or even Vinales) does not want it.

* Rookie.