Ferrari has released an interview in which they state that:
Next year they will not have a first and a second driver, and LeClerc and Sainz will start on equal terms and it will be the track that will decide who will be the captain of the team.
(which is however different in Redbull and Mercedes where they clearly have the two fixed captains)
I believe that this is a good thinking of Ferrari. Because Leclerc and Sainz are both determined and ambitious drivers. They both want to do their best for the team. Moreover, none of them is clearly better than the other one. This makes the competition among them harder. At this point, I also think that it is the best to leave this to the drivers to determine who deserves to be the primary driver of Ferrari.