I'd buy the argument if it weren't for World of Warcraft and its 10 million subscribers.
No, really, World of Warcraft really did change everything. For decades now we've talked, joked, mocked, derided, etc. the idea that someday the folks working in the far more popular and profitable console and PC RPG market would find a way to deliver the fundamental D&D gameplay experience in a manner that could--and, in time, would--kill D&D (and take tabletop RPGs, for all intents and purposes, with them). Folks, that time came and went a couple of years ago; what we're experiencing now is the shockwave of that event finally hitting us.
The new edition is a game that I think will play very well, enjoy considerable popularity and pay for itself. That doesn't mean that I think it's a good move for D&D as a TRPG, and I don't think so because everything that Mearls & company present as a strength is one that World of Warcraft does in a far superior manner with a far superior degree of omnipresence and convenience for a cheaper buy-in cost and an acceptable (if not cheaper) ongoing cost. Why? Because trying to make a tabletop game that attempts to play to the strengths of a different medium, instead of playing to those of its own medium is a sucker's game that always ends in failure. (Where's Eyebeams? He's said as much in his LJ account months ago.)
This is not 2000. This is not 1989. This is not 1977. This is not 1974. This is 2008, and the conditions of both the internal and external factors putting pressure on D&D are nothing like what existed at those prior points in time just before the release of a new edition of D&D. Toss out that 1999 market survey; the conditions then no longer apply, and haven't for years. What we have now, and have had for at least three years, is a truly viable threat to the supremacy of D&D in its own niche! What we have here is a game that does everything that D&D ever did, only faster and better with superior support from a stronger company. World of Warcraft is the first true threat, the first D&D Killer, to come along in the game's history. This is the true, historically-specific factor that too many here utterly fail to take seriously.
What should happen, and won't due to the nature of print publishing, is to refocus the game towards those things that can't be done better by either online networking or by automating the number-crunching. For tabletop RPGs as a business to survive, for the hobby to endure as a cultural force with influence disproportionate to its participants' numbers or its direct influence (and it does have that now) on other media, the game has to shift away from things better done by machines and towards things better done (or only done) by men--by people--and that means doing things like making the known logistical problem (getting a group of adults to agree to block out a set appointment of time, meet on time, work toward a single goal during that time, and do it regularly over an interval of once a week over a year on average) transform from a liability into an asset, or focusing the game away from physical conflict (not just combat, but also the tactical, strategic and logistical resource management aspects) and towards social/emotional conflict. So long as number-crunching and pawn-pushing dominates gameplay, tabletop RPGs are doomed to extinction because computers do all of that far better than people.