isn't mapping technically impossible because of the megatexture thingy making maps weighting something like 200+MB ? (meaning : nearly nobody will download 200MB for a map)
You can make maps without a megatexture - think q4 like maps.
Of course theres nothing to stop you releasing a 200Mb map, and I'm certain people will. Whether they'll be popular on servers (especially as they'll be unranked) remains to be seen.