Most likely the percentage will be much higher. I'm saying that as a former dropout :) I've decided to go through the Machine Learning course (the web version) few months ago but it's really too math heavy. It's not that I'm a total noob but having to parse formulas spanning 2 rows and containing half the Greek alphabet is about as exciting as reading an organic chemistry textbook.
Nevertheless I signed up! But I hope some day there will be a AI/machine learning course that will have code examples for every concept and every math formula, just like this:
Maybe it's just me but code is way easier to read and understand.
I think you're being way too optimistic. I'm guessing about 5% of sign-ups will ever actually follow the course once it starts, and of those, I'm guessing less than 5% of those people will complete the course.