I was just playing GTA:San Andreas and noticed something odd in the background.
The edges of some of the polies at certain distances became blurred which later proved to be some type of post-processing filter applied to them. However, it gave me and idea.
We all know what cubic environment mapping is. Using that concept wouldn't it be possible to draw the most distant portions of a scene onto a cubic environment map texture and then texture the skybox/skydome using that. You would start with the sky texture and then blend in the environment texture like distant terrain, buildings ,etc. Then you would use that texture to texture the final skybox/skydome. What this means is that only the local environment is pure 3D which means you may be able to get away with a lot more polies close up than before.
I'm not sure how it would look without attempting it but I would like to hear some comments.