Even if, between now and January, Congress were to get religion with regard to the benefits to be gained from applying robotics to the transformation of agriculture, and had a full-speed-ahead bill ready for the signature of our new President on the day he takes office, it would still take time for the effect to become evident on the landscape.
To begin with, while you can see the potential for it in what exists today, the technology largely remains to be developed, so figure five years of R&D and experimental installations before anything starts rolling off an assembly line, and probably another five to get the bugs out to the point where it's really possible to let the machines run without some degree of supervision.
At that point, ten years hence, you might still have to drive twenty miles to see one of the new machines in operation. Then, for at least another ten the story would be one of them becoming very gradually more common, as well as more sophisticated. Meanwhile there's mouths to feed, hundreds of millions of them, and business as usual will necessarily continue.
At some point, maybe twenty-five or thirty years out, the size of the market for food cultivated by autonomous machines would surpass the size of the market for conventionally grown food, and at about that time I would expect to see several things happen. For one thing, the largest tractors would disappear from the market, as there would no longer be sufficient demand to justify their production. Also, a shakeout would begin among tractor and implement companies that hadn't gotten into robotics themselves. On the other hand, the infrastructure for getting grain and produce to market could be expected to improve, under pressure from robotic operations with their more diverse output and their ability to provide detailed information about what they would need to move how soon.
Some crops, however, would continue to be more economically produced by conventional methods. In particular, it would be difficult for generalized machines using horticultural methods to match the efficiency of traction-based monoculture in the production of small grains - wheat, barley, oats, and rye. At least in the near term, the reduction in acreage dedicated to raising these crops by conventional methods would result not from direct robotic competition, but from the substitution of more fruits and vegetables in place of grains in the diets of both people and livestock.
Granted, with the advances in robotics that all of this activity would bring about, the tractors on the market then would likely also be capable of autonomous operation, although I'd expect to see a lot of hold-out farmers, using older equipment, still spending long hours driving their tractors, powered by synthetic fuels. Whether that practice will ever become as uncommon as farming with horses had become in 1960 is anyone's guess.