Yup you could blur, but it is not cheap, and it doesn't feel very satisfying to look at blurry stuff in the distance.

We have a "depth of field" implementation for when you're in dialog with an NPC. There it looks nice, because you're focused on one thing. But when looking around its not that great.

Ideally you want it close to native res in the distance, but without any wobble produced by noise as you move. This is really hard.