I bought my 500e from the local dealership near Portland, Oregon, and while the dealership is definitely de-emphasizing their Fiat sales, as you mentioned the California dealerships are doing, when I needed to have the back hatch switch replaced because it was loose and I didn't notice it when inspecting the car for purchase, the service department was very good, and the service techs I talked to were (thankfully) more knowledgeable than I expected, and were very conversant on electric vehicles in general, and seemed excited about the fact that they were continuing with the EV certification process on an ongoing basis.
By the sound of other posts here on this forum, the Mopar service kit includes everything needed for all diagnostics for the 500e, so the question of service will come down to the technicians, which will always be the issue for our now-out-of-production models.
I found the post about being able to Recalibrate the Regenerative Braking System using only an OBD connector and the AlfaOBD app for Android rather illuminating, and gave me an excuse to check with my local service department to ask whether or not this is the kind of thing that can be considered "included maintenance" in lieu of not needing oil changes, but I have not yet heard back.
500e brakes tend to grab a bit when switching from regen to mechanical braking at around 6mph. HUGE thanks to wonderfully helpful members of this forum*, there's an easy fix: On AlfaOBD ($49 version), under ABS>Renenerative Brake Controller>Active diagnostics, select procedure to start (RBC...
www.fiat500owners.com
This is the kind of thing that I expect to be more common, since I don't really have a need for the local service department unless there are other mechanical issues with the car, which, as other people have mentioned, are exactly the same as they would be on a gas-powered 500 or other Fiat / Alfa Romeo cars.