Pontius, here:
https://www.flightglobal.com/news/ar...n-data-419916/
Frankly if everyone has ADSB in and out, what the hell do we need en route ATC for? You will be able to see all traffic and the computer will tag the one that is a threat well before any potential collision.
With no enroute radar if ADSB fails due to a GPS failure ATC won't be much good anyway. Good luck going to procedural control if you've stuffed the airspace with aircraft using lower than procedural separation standards.
This has in fact been simulated in a dense traffic environment some years ago and the surprising result was the small number of conflicts when everyone just flew direct to their destination (Free Flight) while being able to see all traffic. No I don't have the URL to hand.