Would it be better or worse if people could actually talk to other cars on the road? Because, at this point, we've probably reached a point in technology level where we no longer need rely on the honk as our only means of communication.
On the pro side, there could be:
"Your tail light is out."
"You left your gas cap open."
"What's the holdup? Why's nobody moving?" "Because there's a wreck in the intersection."
"All y'all going the other way are about to run into a mile-long jam."
But then, on the con side, there would be:
"You drive like shit." "Fuck you."
Or, for that matter:
"Your tail light is out." "Your tail light is out." "Your tail light is out." "YES I KNOW!"
There could be a way to talk both to individual cars, and to lots of cars at once. But it would have to be quick to pick - trying to type in a license plate number while driving would be a no-go, I think.