I say that you should do a quick sanity check: can you afford to drop out now, and support yourself until your movie is done? If so, go for the movie!
Of course, inspiration level is a personal thing, but I wanted to do stuff like that before and during college. My thought was, I'll get my degree, then start working on whatever pet project had my fancy at the time, and ultimately be able to make a living doing pet projects.
Well, it's been almost five years since I graduated, and I'm still working for the man in a regular job.
Don't get me wrong, I'm not unhappy, nor do I have any regrets. It's just that college put me in touch with an internship, and the internship put me into my current job.
The point is, once you get so far into college, there's a lot of inertia to continue down the "traditional" path.
But you can always come back to college, if the movie thing flops.
It's interesting when you look at some of the world's most successful people---many of them are in fact college dropouts (e.g. Bill Gates).
Other successful dropouts include Trey Parker and Matt Stone, best known for South Park
. If you're not aware, check out their first movie, Cannibal! The Musical
. This is the movie that caused them to drop out of school (i.e. they were spending too much time on the movie and not enough in class).
That's my $0.02.