The 5DII sold well because it was a ground breaking camera with respect to video (full frame!) as well as its photographic performance for the price. The 6D does not have the luxury of being ground breaking in any area.
I think it's a little early to say that. For the longest time I've thought, man they really should put wifi in a rebel body and make it work with Facebook and all the other social networks. I can't tell you how a big a pain it is trying to upload a photo from an slr vs my iphone where it's like two clicks. In this respect I think if they can do it properly that'll be the break away feature. That and the fact it can be remote controlled through an app. I'm sure some creative people will find ways use this with their iPads or such remotely. Could be very interesting. But again... it all depends on how good a job they did on it or if they just threw it together. I was expecting this feature in crop body rebel. But thinking about it now, I can see where they coming from. If they had it in crop body, then all those nice primes they have for their full frame wouldn't frame the same and so it would take away that value added feature. I could be wrong but I'm not aware of any other SLRs that offer this feature. If you true I think this could be a big deal. People can complain about this camera, but honestly it's not that bad. It's not a 5d Mark iii but after the price drops a couple hundred after the initial GOTTA HAVE IT group then I can see this doing well honestly. It looks like it should be at least better than the 5 mark ii sensor albeit less MP but that's fine by me. The higher ISO ranking means even though I have a Mark II, this might allow me to get a 2nd full frame that has even higher ISO capability than mine. The focusing system is at least slightly better. I think the main thing here is we heard rumors of a 7d 19 point system and got so excited about that, just like the D600 people thought it was going to be $1500. When you look at it from that perspective, it kind of sucks but if you just compare it to a 5d Mark ii then it's not that bad a camera. The one feature that makes this DOA for me is if they were idiots and removed AFMA. Hopefully they learned their lesson with the 60D but we'll see.
Canon 5D Mark II, 50D, XSi, 24-105L IS, Sigma 35 1.4, Canon 40 2.8, Canon 35 2.0, Sigma 10-20, Tamron 17-50, Canon 50 1.8, 580 EXII, 430 EXII