They have been working on automated ATC for a lot longer than 20 years. I worked at Eurocontrol 1991-1996 where they had been developing a system called ARC2000 since well before I arrived. As the name suggests it was intended to take over ATC in Europe by the year 2000. I worked on a less ambitious system that helped visualise conflicts for manual resolution but that was not a big priority so I eventually left.