I think you answered this yourself. There are too many variables to gauge an accurate estimate. One of the main ones being the topic of the video, if it is on a subject currently being mentioned in the news regularly, you will recieve a much warmer welcome to Youtube than a specialist subject which is hardly search for.
You give you some quantative data though, my first Youtube video was of myself and my martial arts demonstration team. In the first day, we only had roughly 15 views. Which we were disappointed with. As we added more videos and tutorials etc, our profile grew and now that first video we uploaded had over 200,000 views. Which we are pleased with.
Best of luck for future videos!