I don't think it will sell better then Horizon and I don't think Horizon sold 10 milion, so I think you are a bit off. But I am sure it will do big numbers.
Yeah Horizon Zero Dawn is most likely just barely above 6m atm.
Could God of War be bigger? old GoW Id say no, but this new GoW where they try to make it more appealing to a wider audience... maybe.
Im skeptical if it can reach 10m though, thats a tough milestone to make for any game.
Necro-bump this 2020: http://gamrconnect.vgchartz.com/thread.php?id=229249
Bumb in 2021: http://gamrconnect.vgchartz.com/post.php?id=9047071