Replace? Not anytime soon, but supplement and replace in parts, most definitely, including on crops and in situations where aerial spraying would never have been a goer before. I'd also not rely too heavily on the "it's the law" argument. Laws get changed on a daily basis and a chemical manufacturer who fronts up with all their little ducklings formed up and the requisite 250gb of supporting documentation will get it signed off. It'll all be dressed up in a smart shade of green, ($ and eco credentials), and only reactionary old white men could possibly take on that straw man.