Interesting theories. But I doubt it. Mac Sales were $17.5 Billion last year and climbing. That was 27.25% of Apple's total sales. The MacBook Airs are only iPad like in that they are quick to start and light weight. They are still fully Macs.
However, I do believe the portable Macs will change, in ways that will surprise us. I don't have a clue what Jobs and Ive have up their sleeves at this point. But I will bet that we'll see the results in about 2 years, OS-X will undergo a sea change, and portable Macs will become something we don't expect.
And while most people will scratch their heads and wonder if Jobs has really lost it this time (remember the initial skepticism about the iPad), within a year of that announcement the industry will turn itself around and start copying -that-.