10 million is gonna be hard because times have changed so much since the glory days of God of War and the hack 'n slash genre in the mid 2000s.
Today the gaming market is increasingly about "games as a service", where the target is to force the player to invest disproportionately into just one single game, but God of War just tries to be extremely good quality.
The focus on good story is almost on a level of a quality movie or book, we see a more humane and very likable Kratos and even the boy is very likable. The combat mechanics look genuinely fun. And the graphics are absolutely incredible. And the game is very long for this type of game, like 30 hours to complete I think.
So God of War surely will sell at its maximum possible potential for the type of game it is. Like the OP brought up, the Uncharted games are a good comparison to start with. I think 8 million is within reach.