Here's my thoughts on the current situation, especially with the rumour of no 7Dmk2
'Guinea Pig' is a bit too strong of an expression but overall your point is valid, IMO.
Ever since the 7D was released, it's been obvious that the 7D 'platform' will be shared with a FF model.
From that perspective, the 7D was/is the testbed for this shared 'platform'.
This bodes very well for future 5DIII/X buyers, since they will be getting a camera that's been in field testing for two-three years
I think Canon originally thought that the 7D and its FF brother will happily coexist together.
The way things are going, though, 7D might just get a FF replacement instead of a FF brother.
The Nikon's D7000 and Sony's Nex-7 lowered too much the price of the 'enthusiast' models.
To be competitive with these models, Canon needs to lower the price of the 7DII or beef-up the the specs of the 70D.
The first option is not good for business.
But if Canon beefs up the specs of the 70D, then the 70D will kill 7DII sales - just like the D7000 killed the D300s sales.
So, the rumor that there will be no 7DII makes quite a lot of sense actually.