Modern industrial farming is not sustainable for the next hundred years, no, but there are a lot of levers to work to transform it into something that will reliably feed future generations.

One lever is amount and kind of meat in the average diet. It takes something like seven pounds of grain to make one pound of beef. Modern chicken breeds are amazingly efficient at converting feed grain to chicken meat, but even they are something like two pounds in to one pound out. Reducing the percent of meat in our diets would make our food go significantly further.