Many cars are already connected, in fact. Since GM was mentioned, the OnStar systems, for example, has been in GM cars for more than a decade. It went from analog to 3G in the mid 2000s I believe, so now we shouldn't be surprised if it migrates to 4G. Aside from the emergency features that get advertized on TV, it also monitors several systems in the car, provides directions to destinations, and it provides hands-free telephone service.
Other car manufacturers offer similar connectivity systems. So I don't agree that cars the the last holdout. Also, as we get into self-driving cars, these features will have to become even more pervasive. For example, cars will have to monitor their mechanical and electrical systems well enough to see a problem before it can affect other traffic. And move the car off to the emergency lane if the car is about to become an obstacle. Things like this.
Another ongoing evolution.