I'm going to write a general response as there are just too many specific points to address.
I have to admit, I used "jump the shark" because I think it is an amusing phrase. I can agree that it might not be the most appropriate analogy, but nor do I think it is completely misplaced. As someone pointed out, it just may be too soon to tell.
In that regard, there has been a lot of misunderstanding--as usual--based upon holding too tightly to the letter of the law rather than the spirit. As TerraDave put it, "something has been up." WotC has been steering a wobbling ship - with an unclear course, perhaps because of confusion within the company as to the best direction to take. Does this mean they have jumped the shark with D&D? Maybe, maybe not. But at the least many have observed that they have been flailing a bit over the last eight months or so, and that this means something.
Furthermore, ppaladin123 aptly clarified what I mean by "WotC D&D" and why I used that instead of 4E. I knew this would be a problem, which is why I tried (and evidently failed) to clarify what I meant in the last paragraph of the original post. Let me clarify, again: I am not talking about 4E - that is, the game itself, or how it plays at the table. I am talking about how WotC has handled it, the business and brand name in its current iteration (and I'm not talking about older editions that WotC has published).
I love 4E the game - I think it is the best version of D&D so far, at least in terms of game design and combat, if not in terms of story and setting elements. But, as I tried to communicate in the original post, it is that the way WotC has handled 4E, especially since Fall of 2010, that has been hugely problematic, and thus when I talk about "WotC D&D jumping the shark I am talking about the company itself, or rather the brand group within the company and the direction they are steering the ship. This is not the same thing as the game or how it plays at the table.
So again, I'm not saying that 4E the game jumped the shark, but that WotC's D&D brand group may have, in terms how their handling of the game and the direction they've been going in terms of community and products.