So answer this question, do you ever back-up your computer to make sure you don't lose the important files/photos you have saved??? Having a 2nd memory card slot is the same thing when it comes to a camera! I guess we're not going to agree on the importance of having back-up files!
My point is from a retail price standpoint, I'd much rather have a camera with a 2nd memory card slot and pop-up flash vs. a camera that had one card slot and no pop-up flash, but had GPS and WiFi. If you talk about the "wants v. needs", how many people really need GPS and WiFi?
WiFi = The ultimate 2nd memory card slot, without taking up space in the camera body, and with a great many other benefits as well.
Computer back-ups are great, if you keep them off site. If they're in the same building, then they're only so-so, since if the place burns down, everything goes. Same with having two card slots in the body - drop the camera over the side of the boat, and it doesn't matter if you copied to both cards. But with WiFi, your laptop sitting safely in the corner can still have your images.
Sounds to me like Canon is trying for a paradigm shift in this area.