Chances are quite high for the future cause both, Apple and Audi (as well as other car manufacturer), are member of the car connectivity consortium that is currently working on the digital car key
https://carconnectivity.org/press-r...ry-standardized-smart-phone-car-key-solution/
Combined with Apple Watch this would be awesome! And of course gets even better when you are able to transfer spontaneously the key of your car over internet to another family member or if you plan to use Car-Sharing or want to rent a car at the airport etc.
Audi already released kind of release 1 digital key for example in the Audi A8. But you need an Android Smartphone to use it.
https://www.audi.de/dam/nemo/models/misc/connect/PDF/Audi-connect-Schluessel.pdf
Release 2 completion is already planned for Q1 2019 and from then it should be ready for implementing.
Best of all: Contrary to cashless payment, this solution is predestined to start in Germany first and not after 4 years!!!