You can improve jpeg noise reduction with a faster cpu and better algorithm, and you can lower banding with better readouts. The 70d might also get a better noise pattern like 5d2->5d3. And you probably can bump dynamic range a bit with the same sensor tech (see minor dr increase 5d3->6d) - but that's about it.
The press release downplays the BSI sensor, while hyping the new Digic 6 processor.
Just consider that Canon doesn't have BSI technology in-house.
So, the sensor is sourced from someone else (Sony?).
At the same time, Digic is an in-house technology for Canon.