What's funny about this is that until there is widely accepted V2V communication, the opposite will be true. You know how you drive on the freeway during rush hour and most people are driving 70mph+ like 2 car lengths away from the car in front them? An autonomous system will say fucking nope to that and drive much more cautiously. That's a good thing, but the space required for an autonomous car will be larger than a meatbag car for a long time because they are going to be cautious.
When you have a large adoption of autonomous vehicles, you'll see an increase in traffic because they're all going to be spaced out a bunch, accelerate slowly etc. These are just growing pains, but we're not going to see this majestic chorus of vehicles for a very long time, if ever.