As long as Canon keeps selling the 50 f/1.4 and 85 f/1.8 like they have been, I think we'll be in for a long wait. Those lens productions must be almost pure profit at this point and while they aren't the world's best lenses, they are good enough for a great many people. The 24, 28, and 35 lenses were rather poor in comparison and not good sellers from what I understand, so the economics to replace them made sense. Sigma certainly hears the voices of discontent, however...
This is pretty much what I think as well. The 50/1.4 and 85/1.8 are great as they are so the improvement will be harder to sell at a higher price point. Canon knows that the ROI for a prime lens factors heavily into pro shooters' decisions and many already own the existing 50 and 85. Canon must find or somehow create a demand for the replacement versions and that was a lot easier with lackluster 24, 28 and 35 version 1 lenses. And while they're at it, Canon doesn't want to create an EF lens that is so good that the L versions become less of an upgrade at their even higher price point!
I assume zooms probably sell much better at a higher price point so they get all the love first.
Incidentally, I don't agree that Canon doesn't foresee a market with newer versions of the non-L 50 and 85.
Regarding the 50, there is certainly a large number of videographers who will like a 50 IS, and if Canon can bring out even a 50/1.8 IS sharp wide open and prices it at $ 600/700 then they clearly leave room for the 50L (a full stop faster for the bokeh people and dedicated portrait users), while they still allow the cheaper 50/1.4 and much cheaper 50/1.8 to sell.
Regarding the 85, there is a large amount of people who can use a faster focusing medium telephoto, and will prefer better color and contrast that what the 85/1.8 provides. Now, an 85/1.4 priced at just about 1K will affect both 85/1.8 and 85/1.2L sales (although breaking up the segment might increase net sales as a lot of 85/1.8 users will upgrade to the 85/1.4 and at that point it becomes a numbers game). What I think more likely is Canon upgrading the 85 to a 85/1.8 II and pricing it at ~ $ 800. That will let them make more profit on the f/1.8 bracket and not affect the 85/1.2L too much.
We will see I suppose.