To say that they took a leave of absence would be much more disingenuous than to say they dropped out; none of them is thinking of returning to college.
I'm not sure about that - I think it's fair to say that none of them is thinking of returning to college anymore
. But let's face it - if Microsoft or Facebook had failed miserably, it seems highly likely that Gates/Zuck would have returned to Harvard to finish their degrees.
Indeed, that's why starting a company for them was a relatively low-risk affair. What do you have to really lose? If the company fails, oh well, you're simply relegated to a consolation prize of a degree from Harvard. Boo hoo, such epic tragedy, cue the world's smallest violin.