Yes, the tech to farm without farmers is getting scary good. But, equipment maintenence takes people, and machinery breaks, gets stuck in mud, has to switch implements (hook/unhook hyd hoses/electric cables). So, terminator will have to be good enough to do those chores.
Crop duster pilots are probably wondering when drones will be doing their jobs.
Within five years, max.
Watch the embedded video...
DJI Agras T30 Agriculture Drone
Here's the newest DJI ag model on YouTube: Agras T40
This is a great video by Taylor from AgriSpray Drones. He shows how to program, set up, and use the DJI Agras T40 in the field: DJI Agras T40 Full Spraying Demo