The two things that the 6D is lacking that I think are important to a amateur/prosumer photographer are a second memory card slot and a pop-up flash. I just purchased a Nikon D600 for my father, rather than the 6D, because the D600 had the second memory card slot and a pop-up flash.
I could care less about WiFi and GPS....and video for that matter! I think Canon should have designed this camera geared toward purely still photography, and left out the video, which would have kept down the retail price and Canon might have been able to price it around $1,500. The Nikon D700 doesn't have video, and look at how many still love that camera!
I agree regarding the pop-up flash. However, the only reason I want one on my 5D3 is to be able to use it a wireless trigger. Other than that, I see little to no value to it.
As for the secondary card slot...
I don't see why people are complaining so much about it. I have a CF card and an SD in my 5D3, but I never use em both at the same time. I did once, and regretted it during post processing.
I only use the SD card when my CF card runs out of space.
Wifi on the other hand,
Nikon sees the potential of including that technology. In the commercial for the new D3200, they advertised their wifi dongle to go with it. The first guy I met using a D600 (before it became widely available), showed off the wireless dongle to me as one of the features he liked about it. It is a great feature to have when shooting sports b/c you don't have to buy an Eye-fi card to send the photos wirelessly to your computer. His D600 had some kind of compartment on the strap to house the wireless dongle.
Not to mention that a LOT of people out there take pictures and then post them to Facebook, flickr, etc. Canon is going to release a phone app (for iOS and Android) that allows you to control your DSLR with your phone. The phone can function as a wireless release and even upload the your camera's photos online without the need to download them to your computer.
The real kicker would be if you can use your phone as a wifi hotspot. That means you can post the pictures ANYWHERE that you have cell reception. I can see lots of teenagers and young adults using this feature to upload their photos to facebook and whatnot.
Yeah, WiFi might be a good idea for an entry level DSLR or point and shoot, but I don't see a lot of teenagers and young adults buying $2,000+ DSLR bodies, and I doubt most people that buy a $2,000+ body will post their photos on the internet without processing the RAW files on their computer first.