I'm not sure if enough hype is surrounding the game for it to hit the mark. I haven't been following it that closely, but I think if it were likely to sell 10m, it would have more people talking about it.
At the same time, this isn't in any way an objective observation. It's just how I'm feeling. The series has been kind of stagnated IMO so I think it'll do 5m at most.
(Just going to add here that I haven't been following gaming as much recently so I could be totally off about how much people are looking forward to this)