Video Game Consoles are a perfectly valid comparison. How many Gamecube games have come out in the last year? How many new AAA PS2 games (not shovelware, not 2 year old translated imports, etc.)? The PS2 has sold 115+ million units....sure there will be some new games coming. But
most of it is stuff just being shoved out the door to a desperate audience. The PS2 is widely regarded as having had it's last hurrah, the Gamecube and the Original Xbox have both been abandoned.
But that doesn't make the consoles any less useful. The PS2's back library is HUGE. And claims that old games won't sell is nonsense. Just last night, I purchased Super Metroid on the Wii's virtual console, which has seen fantastic sales this year. Sales of updated games on Xbox Live Arcade and the Playstation Store of old games is brisk. Sales of old games is as strong as ever. The same is true of 1e, 2e and now 3e...except that unlike those platforms, with D&D
you can actually generate your own content. Better yet, you can continue to exchange it with other enthusiasts.
The idea that 4e is 'too soon' is a personal judgement, and will vary for each person. The idea that significant advancements couldn't be formulated in even a simple two years is, to me, ridiculous. ENWorld is rife with discussions of things in the rules that people are constantly discussing the validity of or new mechanics they've created. The whole benefit of the SRD and OGL was the creation of just that sort of thing. Look at Unearthed Arcana: some of those concepts came from 3rd party development. Look at all the interesting mechanics such as Incarnum, Reserve Feats, Teamwork benefits, Legacy Weapons, the 9 Swords combat system and more (let alone the ideas from the Saga system, Iron Heroes, Arcana Unearthed and True20 systems that have filtered into the core). More people have been working on improving D&D (consciously or not) more than ever before, and have been interacting more than ever before.
I was guarded when I heard the announcement, but everything I've heard since then evokes the same feelings I got when I picked up the 3e PHB seven years ago on a whim (with no expectations of returning to D&D). That the new editions chief developer wasn't playing D&D when 3E was in development should show you how far we've come.
Now, if you feel WotC is doing you the dirt, then vote with your dollars. Don't buy 4e, and support people who are still releasing 3e and try to convince others to do the same. With the advent of games like C&C and OSRIC, it's clear that older editions will always have some level of support, especially via the 'net.
I personally look forward to an edition that refines everything I like in the 3e/3.5e and improves it. It's possible they'll fail, of course, but I haven't been disappointed with the last two editions, so I'll continue to be optimistic. YMMV.