It all depends on whether there are enough 4K households. Consoles never target the elite, they are mainstream products. Wouldn't make sense to make the product a lot more expensive for 4K when only a few % of their users can enjoy it.
That said, if next gen starts in 2019/2020, the consoles will have the equivalent of mid to high end gpu's of 2017/2018. So if in 2-3 years there are $200-250 cards that can easily take on 4K at 30fps, it's prolly what the PS5 will be able to do.
I guess there's gonna be a fair bit of 1440p/other weird resolutions too.









