Ducati is not saying yet, but it seems the riders on their payroll will be:
Jack Miller: Confirmed Ducati Factory
Jorge Lorenzo: Ducati Factory (just a rumour, but Ducati boss did not deny and indicated there are possibly discussions)
Pecco Bagnaia: Ducati Factory if not Lorenzo or Zarco, otherwise continue at Pramac.
Jorge Martin: Confirmed Pramac Ducati
Zarco: Avintia, maybe Pramac with one of those named for Pramac in Avintia.
If it was me making the choice I would select:
Ducati Factory: Jack and Pecco
Pramac: Jorge and Jorge
Avintia: Zarco