Or have 4 copies of each map (designed to look like they have been rotated 90 degrees from each other) and some how track what happens on the other maps and modify the 3 "hidden" maps while you play on the one active map.
The first post says that the deserts will be added into the game in Version 13 (29th July). But you will have to wait until someone does an actual map with the desert tiles. (assuming Chris hasn't slapped on together himself)or for example if you launch a mission in the desert will be the desert tile?
Edit: (also assuming Chris has added an identifier to the geoscape for deserts... most likely he will have done that.)
So that would be V14 when the first batch of maps from the designated level designer is expected.
Short version: V13 If you make some maps yourself. V14 If you wait for official maps.