First off, I'd like to point out that there's no reason you can't do both. While I was at college, I built several successful projects, conducted research, took jobs and interned in my chosen field (computer security) while working towards a computer science degree. For me, ultimately, the decision to drop out and take a senior position in my field was something I couldn't pass up.
That said, I've always heard and respected the opinion that dropping out to run towards an opportunity is different than running away from, say, classes that you're worried might not be super relevant by the time you graduate.
On one hand, you're right--fields change very quickly, and surely your sophomore classes will seem dated in three years when you land a job in your field. However, dropping out will present challenges later on. I, personally, have been lucky enough to not run into many obstacles because I don't hold a degree--primarily because the companies I've worked for do not place huge amounts of stock into a degree--but many other organizations would.
For now, stay in school. Learn your trade. Work on side-projects so that you have an impressive portfolio when you graduate. If it doesn't work out, or if an opportunity too good to pass up presents itself, jump on it. Don't drop out for the sake of dropping out. Besides, college is a great place to network with people whose connections may be invaluable some day.
Also, and this probably goes without saying, this decision is ultimately up to you. Asking on the Internet about it will not make up your mind, nor can random HNers, as intelligent as they may be, tell you what to do. The above comment just consists of some thoughts I have on an issue that strikes close to home.