In reply to mark k..

I think you answered your own question, most users aren't going to read anything you put in front of them. The more complex the process comes the less people will engage. If they aren't engaging now, adding further notifications isn't going to aid the situation.

Just upgrade and release your plugin. They get what they are given and tough luck if they don't want it and didn't read the upgrade notes, who do these users think they are!