Where I live, if you have a bachelor's degree already, you can go through a training program for a few months to become certified as a teacher. So no, you don't have to be an education major in college to teach.
Some college students these days take courses online, but there is still a professor for that course you can meet "live" with from time to time, so its not like their jobs have been eliminated because of online courses. I took college algebra online, and met with my professor frequently during the semester. And for young students (under 18) its not ideal for them to learn only on the computer all day long. I feel they need regular interaction with an adult in a classroom environment. Just my opinion, anyway.