Vettel's contract at Maranello runs out at the end of the 2020 season, but he has been rumoured recently to be considering retirement from the sport.
Ricciardo has a two-year deal at Renault, after joining at the start of this season from Red Bull. Mercedes and Ferrari considered Ricciardo for the 2019 season, but decided against and the Aussie driver may be cautious when considering his options as he firmly believes in Renault's long-term targets.
Bottas sees his current deal at Mercedes run out at the end of this season and Toto Wolff has already stated that the Finn "knows he needs to perform" to keep his seat at the Silver Arrows next season. Esteban Ocon is the reserve driver for Mercedes and he has been linked with Bottas' seat.
The pair will be top of Ferrari's wish-list and the backroom staff at Maranello will be eager to try and find out Vettel's future sooner rather than later.