They want to sell a million of Shenmue III, which is doable. Quantic Dream's games sell more than that, Life is Strange sold more than that, etc.Is it at all possible that a Shenmue 4 or 5 could be produced? How is Shenmue 3 expected to sell? How did the first two games sell?
First Shenmue sold pretty well actually, over a million worldwide when there weren't a whole lot of Dreamcasts sold. I think someone likened the attach rate to something like Skyrim. Second didn't sell great, but I think that can be easily blamed on it releasing after the Dreamcast was pronounced dead, and how the game was delayed and only released on Xbox in North America.
Can a Shenmue IV and V happen? Sure. Making Shenmue III happen was the hard part. The series now has renewed relevance and can hopefully attract a bunch of new fans.