There isn't a lot of geometry? Though geometry itself isn't that limiting anymore, unlike shader effects alltogether, it depends on a lot of things. Will Zelda have actual physics? how much AI is in there? How much does it load on one time? There's actually still a ton of things that can make open world games much CPU heavier. So there's that limiting factor.
And there also is the GPU. Looking at what we've seen there will be some fx more or less absent. Others seem really good.







