I'm with you LipeJJ. BotW is going to sell far more than any Zelda that has come before it. Of course, people already told me I was nuts for saying it would outsell Odyssey. I expect Zelda to have some serious legs though, while Odyssey sales levels will fall back down to what 3D Mario normally does.
In the end I think 20m is a good ballpark for Zelda. Not sure if it will actually cross that line or come in just shy of that though.