there will still be brakes, suspension, wheels,tires,  bearings, hoses, A/C etc. to service.

It's just that mechanics will need to electronics on top of that.

I wouldn't say they would be out of service-yet. There will be replacements because somebody has to work on the cars in the shop.

Recently I've noticed that "mechanics" are starting to become "technicians" as cars these days are more electronically controlled than mechanically controlled, so it's very likely that the term and the idea of the "automotive mechanic" will be phased out entirely in the next 20 years and fully replaced with the term "technician". However, I highly doubt they are ever going to get rid of the dealership mechanics/technicians, because that's where a lot of their revenue comes from.

And yes, I do think that almost every mechanic will eventually be out of a job due to there being less and less older cars on the road as time goes on (Let's try to save as many classic and older cars as we can!).

Anything and everything will eventually break, electric vehicles still have most of the system diesel and petrol/gasoline cars do (brakes, suspensions, etc) ... As long as we have vehicles we will need mechanics to work on them. Existing mechanics may need to learn new things, but will certainly be an important resource. Scotty is a great example, he's been working on cars since before fuel injection was common. He now uses high level scan tools to diagnose vehicles for problems that may not have existed when he started his career.