Which college majors will be the most valuable in our society 20-30+ years from now?

This will by no means be a comprehensive list with research to back it up, but here is my personal list (in no particular order):

Agricultural science: As the human population surpasses the 10 billion mark and environmental change seems more imminent than ever, countries from all economic strata will fight to recruit the talents of agricultural scientists and their arsenal of radical new GMOs and other “green” technologies, lest their people go hungry the coming drought season.

Biomedical engineering: There will come a time when we ponder why we submit to toxic pills and nuclear radiation to cure cancer when we can just throw out the damn organ and implant a freshly printed one from our own personal organ banks! Additionally, with technological advancements across the engineering disciplines, we as humans will see the “transhumanism” philosophy validated more and more as implants serve as worthy substitutes - and even extensions - for our bodily functions. I personally predict that blindness in the eyes will be completely curable before 2050.

Quantum computing/CS: We will only be able to pack so much computing power into our microprocessors, even with new materials like graphene and clever 3D arrangements within the chip architecture. But if quantum computing can provide a stable, error-free computer that provides a tangible speed up to all classes of algorithms, then we have a real winner on our hands. Applied quantum physicists and other engineers will create the Intel of the 21st century, and researchers spanning theoretical computer scientists and information theorists will quickly reconvene to be able to extend and capitalize on this awesome new technology. People working in the fields of AI and machine learning will see massive benefits as well, in the form of explosions of development in their respective fields, and those who are on the forefront of this achievement might very well control the world.