Meh. My table has six subscriptions - which is one more than last year. That's 20% growth.
And I don't even read the articles.
PS
Agreed, out of the 4 players in one group and 3 regulars in my other group, plus me, we have a total now of 3 active DDI subs that I know of, and I THINK one of the other people has one as well, but I'm not 100% sure. That's up from 5 players plus me with 2 subs total 3-4 years ago.
Remember, while some people may find DDI to be PUTTING OUT less stuff now, it has MORE STUFF EVERY YEAR, because nothing ever goes away. This is part of the reason I think the "magazine format" is kind of a mistake, it causes the wrong measuring stick to be used. It has good points too, but still. The other aspect is that there is a lot more stuff. 4 years ago you could just play and you had 3 core books and 2-3 supplements and a few Dragon articles. It wasn't hard to keep track of, and you could just build your character (and old CB didn't really require a subscription once you had it).
Come back now today and there's a vast array of stuff that CB and Compendium helps with, and a HUGE library of stuff on PDF in there from 5 years of Dragons and Dungeons, so why not sign up? Even if they DO put out a bunch less new articles every month you still have all that stuff to go through. (and yes, in theory you can download it all in a single month, good luck!). Overall I think it actually does make sense.
I'd also like to point out that there's no reason to believe that the number of people actively playing 4e has dwindled either. Surely as the game has become well-distributed and known the sales of books have fallen off. This is not at all related to how much the game is played. If you go to an Encounters or LA session there's plenty of people there. I have PLENTY of players available for both my online and offline groups. In fact I have more players right now than at any point except maybe one brief moment in 2008, but these are all ones that show up and play reliably every week. We buy far fewer books, more DDI, and play more than at any point in time. Its all anecdote, but I see no reason to believe that DDI should be smaller now than before or that it is a worse deal now than before. Quite the contrary.