Ubisoft's definition of a mid range rig and the definition that a hard core gamer would use are two totally different things.
As I understand it, SHV is being optimized to be more efficient than SHIV, and 2 GIGs of RAM will run it perfectly smoothly. A dual core processor at 3 GHz running with a mid range 512MB video card will also run the game smoothly... at the lower end of the screen resolution scale (1280 X 1024)
Ubisoft knows that about 90 percent of the people who purchase this game are not members of Forums like this, and they are not going to upgrade their computer in order to play it. So in order for Ubisoft to make money, the specs for this game will be a little higher than SHIV, but not radically higher.
Simple as that really.