To know what the speed limit is, the car will have to know what road you are on. I assume this means constant tracking of your route, which means constant contact with a GPS service. Someone will know where you are at all times.
The ACTIVE system will come next. Control of your gas pedal by the car's computer, or via telemetry through the GPS service and law enforcement. It's so handy to slow or stop a vehicle without spike strips that LEO's will have this capability in their cars eventually. No more high speed chases!
So glad the last car I bought has no telemetry whatsoever. I drive it until it dies, or I do.