That "10 times" bandwidth number they are tossing about is the theoretical maximum increase in bandwidth.
A lot of the performance increase will be tied to how well the data is organized in memory. In reality, the performance increase will be much less, but more than what is currently available. What the "real" increase will be is a best guess, at the moment.
Still, it is a nice idea and will save a ton of real estate and power, while offering an easier method to increasing the amount of memory on the card. Good stuff.