I suspect one of the bigger issues with automated ATC is you will always need human controllers to be there to take over when the automated system fails.
Moreover, since the job of an ATC controller is a difficult one that requires a great deal of mental dexterity to translate a two dimensional display or moving object information into a mental picture of a three dimensional airspace, the individual really needs to be active regularly enough to keep those skills sharp.
There is no doubt a computer can monitor and extrapolate how traffic is moving relative to one another far better than a human can, but the whole communication with a human thing is another story. It might work great as long as everything was operating routinely, but odd things happen quickly.
As such, you sort of want it automated but at the same time... you don't.
I rather suspect, and hope, that instead of going down some fully-automated route, the tools presented to the human ATC will improve instead.
How that blends into moves to use pilotless aircraft.. I have no idea.