I think you over estimate how much apple relies on "making the old model look old and dated".
My 2011 Macbook Pro 15.4 looks remarkably similar to my old 2006 Power PC Powerbook. The 3GS is one of the best selling smart phones on market even though the form factor was set introduced in 2008. There was some compelling analysis a few months ago that made a compelling case that iPhone 4 sales were constrained by the ability to manufacture them.
It's possible I overestimate it. And I don't mean to say that it's their driving motivation or anything. I do think it's some significant part of the calculation.
Laptops are a different market. You have your phone on you all the time so it works much better as a signaling device, and it's only ~$200 to upgrade.
The 3GS sells well at least in part because it's less expensive. The ones you're targeting with design obsolescence are the high end who will pay again for the high end.
I've already seen comments around here to the effect of: "Hm, just an internal spec refresh. Guess I can wait until the iPhone 5."
My 2011 Macbook Pro 15.4 looks remarkably similar to my old 2006 Power PC Powerbook. The 3GS is one of the best selling smart phones on market even though the form factor was set introduced in 2008. There was some compelling analysis a few months ago that made a compelling case that iPhone 4 sales were constrained by the ability to manufacture them.