Here's the tough to accept fact Dilbert. Canon doesn't really care to have you as a customer.
That's quite ok.
It's all about conversion costs.
Well, Sigma are working towards making it easier with lenses that can be adapted.
Would Canon like for you to buy a 5DIII. Well, in an ideal world yes. But they have to look at what it will take to do that. You take way too long to make a decision, you don't spend very much and after the sale you are likely to be a high maintenance customer.
There's a lot of speculation and comment there with no basis for fact.
So, it's basic business sense that it's better to concentrate on customers who want to make a purchase, are going to make that purchase in the near future, are likely to make additional after-sales purchases and are likely to be content with their purchase decisions.
They're called "fan-bois" and will do whatever Canon says and buy whatever Canon makes.
You want to get the most for your money. So does Canon. They look at you (actually the profile of hundreds of customers like you) and compare what it will cost them to convert you to a buyer. They compare the cost to convert you to a buyer to the cost of other buyers, including existing customers, and focus on doing what it takes to attract interested customers rather than theoretical customers.
That's actually the most intelligent part of your whole post. It would be interesting to see the sales volume of the 5D3 vs the 5D2 over time and if X% of 5D3 sales are upgrades, how many haven't upgraded.