The only way to prevent midair collisions in my opinion is this:
We need special goggles or eye glasses that can highlight traffic to enhance our normal vision.
It could work with the ADS-B to track each aircraft position in space. But instead of staring at the panel, the pilot would be looking outside.
And traffic on the left side, for example, would alert the pilot with a sound in the left headphone. Then the pilot would turn his head left and see the traffic with his enhanced vision glasses.
Anything less than this for NextGen is a waste of time, money and lives.
slowrotor