If Ogier was to simply just lose the championship in a close fought battle I dont think he'd leave. But as others have said, if by the end of the season he's miles off Tanak, and Citroen cant give him guarantees of when/if the car can be improved massively, then yeah I think he'll have a decision to make over whether 2020 in a citroen is worth it...
They've been working on aero improvements since December last year and still nothing, for example...!