...why the need to take potshots at them right off the top?
Who is taking "potshots"? I'm not making any qualitative judgements about 4E as a game - I like it, play it, and prefer to other editions of D&D, including Pathfinder. But I think it is almost a self-evident truth that 4E is not as successful as WotC would have liked it to be, both economically speaking but also in terms of the community, which is fractured in a way that it has never been.
With some of the things Mearls has been talking about lately, and DDI being the future of D&D, I don't think new editions are a necessity or inevitable.
I can see an ever evolving DDI based game. New ideas are incorporated, rules are modified, approaches and emphasis are shifted, and the game slowly morphs from month to month, year to year, and a new edition is never actually developed. 10 years from now D&D will look a bit different than it does now - but it won't be called 5E.
Even more, I expect that mention of editions (except in a historical context) will eventually disappear also (officially - not necessarily by customers). You'll have rules online set up in various degrees of complexity and approach (simple and fast, complex, simulationist, story telling, tactical, etc.) - an
ala carte RPG courtesy of online DDI.
I don't disagree with this and have had similar thoughts; I remember starting a thread a year or so back about DDI being the new core.
That said, I think there will always be new print runs, "state of the game" editions, so to speak. And the easiest, most clear--and probably most money-making--way to differentiate these print runs is through new editions. The difference being that the online version will always be the most up-to-date; this is already the case - compare, for instance, the 2008
Player's Handbook with DDI right now.
Who is 'they'? Who is coming up with some wildly divergent idea for D&D, and why would he be so opposed to it they need to remove him?
You know..
.them.
I suspect you've got several much more likely possible reasons:
1) Layoffs were coming for coming, for whatever reasons. As is often the case, a senior employee might volunteer to leave, knowing that by departing with their higher salary, it would mean not having to cut 2-3 staff members lower in the ranks.
2) Alternatively, this involves a follow-up to the reorganization from last year, when they split into the board game and RPG divions. The context of that different approach might have resulted in some positions not being as needed, or needed in different ways.
3) Or this may indeed be blowback from a failed initiative. I don't know one way or another if Essentials has 'failed', but if it did end up getting oversold to management, and ended up underperforming, the blame might end up hitting up high.
I don't know if any of those are the case. But it doesn't seem likely, to me, that this sort of thing would be indicative of 5E being on the horizon. It actually seems evidence that isn't the case, since I don't think, if there had been any forward momentum on such a thing, that they would disrupt it midstream in such a fashion.
Hmm...I don't think this is necessarily true. If WotC is restructuring to prepare for a new edition of the game to begin serious development, with a scheduled publication in, say, 2-3 years, why wouldn't they clear house a bit? Especially if they want to bring fresh minds on to design the new edition?
There is also the question of how much staff is needed to run WotC pre-Essentials when they were churning out tons of books, versus now when meatspace products are fewer but DDI is the focus. Maybe they've found their DDI sea legs and realize they don't need as many folks to run the virtual ship.
I'm open to any theory at this point - my point is only that we can interpret the data in various ways.
I'm not sure that is a large enough sample size to make any really accurate predictions... especially given the different contexts of some of these editions.
Who said anything about "really accurate"?

Speculation is fun because it doesn't have to be accurate at all.
I mean, my one theories are only a year or two behind yours - I don't think it impossible that 5E is approaching, just that it isn't especially close, and that all these current 'signs' and 'evidence' have basically nothing to do with it at all.
So you don't think that Mearls' recent series of articles has nothing to do with 5E, that he isn't fishing for ideas and feedback?
I strongly suspect 2014, to coincide with the 40th anniversary of D&D.
That's a good point - I hadn't thought of that. Given that fact, I'm feeling a bit more strong in my suspicion that 2014 is the year that we get the "40th Anniversary Edition" of Dungeons & Dragons. Knowing WotC, they might try to get away with it not being a new edition but everyone will call it 5E, even if they don't!