God of War has sold 90k in the UK according to estimates which is 35 percent more than God of War 3. God of War 3 sold 1.2 million in its first week and 5.2 million in 2 years. If God of War sells similarly compared to its predecessor in the whole world that would be 1.62 million debut at retail. God of War 3 wasn't released on PS Store on PS3 ever while God of War was released day and date on the Store and it has known short supplies in the US, UK and many places around the earth.
Horizon sold 3.4 million in 2 months and 915k of that was digital sales. That is 27 percent of its sales and it had no stock problems. God of War does have stock problems and its released in 2018 when digital sales are higher. I would say its sold 40 percent digital. That would put its first week total at 2.65 million, right around Uncharted 4's first week sales of 2.7 million. If we go by God of War 3's first week to 2 years sales ratio, God of War will sell 11.5 million.
God of War 3 sales source: https://www.sony.net/SonyInfo/IR/news/120605_05.pdf
These sales were as of May 31, 2012. God of War series sold 21 million till that time. It was before the release of God of War Saga, God of War: Ascension, God of War 3 Remastered and God of War.