Well, that's still 80Mbps, which is 40 times what I had back in ≈2005.
Whenever there are texture updates, there will be huge updates if they add new or swap out the old ones. I can't think of any other way to do it. Maybe someone will come up with some sort of dedupe tech down the line. Maybe when the world map drops some sort of stream/cache can be achieved for the standalone maps too.