Hrm, how to reconcile these two points of view? Both pretty much entirely based on anecdotes with no context. On one hand, syaing that WOTC's fan base got smaller is a complete assumption with no factual backing, but, on the other hand, "tons of people have a DDI subscription" isn't exactly scientific either.
Guess it's back to the three blind men and an elephant time again.
There are basically a few data points we have:
1) Industry info, not quantitative, but presumably the purveyors of this information manage to sell it to someone, so it has some value...
2) Amazon sales figures, questionable to draw too many conclusions from, but still indicative.
3) The actual WotC product releases. Hard to say exactly what they tell us, but we know that WotC is still turning out D&D stuff...
4) WotC staffing. We don't know for sure what this is, but we can at least tell when they add to or cut back from staff.
5) Size of the DDI group on the WotC boards. We know objectively this represents the lower bound on current active DDI subscribers.
1 & 2 both still put 4e in the top 5 RPGs and often in the #1 spot. 3 obvious shows they've changed focus, but equally obviously they are still releasing a decent amount of stuff. 4 appears to be unchanged for well over a year. 5 is up to 50822 members from 48k in Feb.
I wouldn't go out far on any ice and say this all tells us exactly what is going on or that any great conclusions can be drawn, but it is pretty plain that 4e is competitive with several other RPGs, one of which is its own evil twin. Hasbro apparently feels justified in maintaining the staffing for the product and producing a reasonable amount of material even if the mix is a bit different than it was a while back. Finally it is pretty clear that DDI has a fairly steady user base that appears to probably be growing slowly over time.
Nothing I see anywhere in any of this indicates a product in some kind of collapse or death spiral. People have claimed that "Essentials tanked" but again there isn't even the slightest evidence to back that up. The product is out there in a LOT of retail outlets, which seems to have been a major objective, and it appears to remain on the shelves, unlike many of the previous hardbacks which have slowly disappeared.
Aside from unsubstantiated statements by people that don't work for WotC and presumably don't actually have any more information than anyone on this forum D&D 4e appears to be doing OK. That could certainly be untrue or 'doing OK' could be unacceptable to the money people but AFAICT anyone claiming they know more is blowing hot air. I'm comfortable holding the opinion that the game is viable and will largely go on as it has, modulus some shifts which really are in no way unprecedented for D&D in its history.