I have the same opinion about using the same sensor.... for me a basic upgrade for a body must be the ISO performance (that I guess will be the same).... Imagine if they would have kept the same sensor between the 5d and the 5d mark III... it would have been a disaster.
BUT, this camera probably is not meant for me, meaning that, as stated by other user, people would care more for sharing in FB than ISO performance.... well, that is call entry level.
Let's see about the sensor in the 70D and the 7D mark II (if they are finally coming).
Victor