From the images I've seen even when you have the new feature you'll still get some that just show the grass because there's no pokestop nearby.
So for people outside of cities they'll basically just have the current grass tracking
![Stick Out Tongue :p :p](/styles/default/xenforo/vbSmilies/Normal/tongue.gif)
.
Edit: they could make it so that even when it's just the grass you can click on it and it zooms out and just shows a circle or something on the map showing that the pokemon is inside that area instead of showing the pokestop that it's in range of.
This is what it looks like when there's no pokestop in range for some: