I used to have a 7D. A camera I took many pictures with and really enjoyed. But I was using it mainly behind L series lenses because I wanted the quality that those lenses provide. This has proved to be a good investment as I now have a 5D3 and a 1Dx and the lenses work with them.
I don't want more megapixels, I've got more than I uses almost always. And before anyone suggests it I certainly don't want more just so I can crop them away.
One of my main problems with all this kit is the weight, carrying 40Kg on a trek to a wild life photo opertunity can be a pain.
When the 7D2 comes out the thing that would get me to buy one would be if light weight lens were available with similar quality to the L series but making use of the reduced diameter needed for the smaller sensor. (While they are at it they can reduce the price as the elements aren't as big. )
I know its not going to happen but it would be nice if it did. ------- Just think a nice quality 200-400 with built in 1.4x at about 1/2 the weight and cost in front of a crop sensor giving equivalent view to a 300 to 900 on a FF.
( BTW There can be little doubt that someone who thinks they know better will ridicule this idea. If they convince me that they are right I will claim I was being sarcastic )
You must have quite a outfit to weigh 40KG (88 lbs). Most bodies and lenses are in the 2-3 lb category, the big whites weigh more, so if you used a lot of lenses like the 400mm f/2.8, the weight would add up.
A "L" quality 70-200mm f/2.8 EF-s will be smaller, but the "L" treatment with high density glass and fluorite elements will add weight. It takes more and stronger material to hold those heavy elements securely, and soon there is little weight savings and no cost savings.
IMHO, I really doubt that there is a market for a $1800 70-200mm f/2.8 EF-s lens. Most would pay the $400 extra for a FF, because they intend to get FF in the future.
I agree with much of what your saying and don't expect it to happen.
But although I would expect the saving in money would not be much I do think the saving in weight could be significant, and in size as well come to that.
Also forgot to say, yes I'm carrying a couple of ff bodies and several big whites plus tripods flashes a hide a chair, it all adds up.