I think most SEOs take into account the other search engines too. I can't remember where I heard it but something that has stuck in my head has been you need to flex your SEO muscles down the GYM - Google, Yahoo, Microsoft. They all employ different ways of scoring your site. If you optimise only for Google does that mean you want to ignore the other 40% of the market?
But Google will never die if then it will be just a new mutation. We will get a high version of Google by Google.