Consumer level Desktop PCs may be on the endangered species list, but they will most definitely stick around in the corporate and academic worlds. It almost seems like Dell is ready to ditch the average consumer market by phasing out the Dimension series, you now just have your pick of four Inspiron systems, 2 AMD, 2 Intel. If you want something else you gotta go XPS series where again you have a choice of just four systems. XPS One, XPS 420, XPS 630, and XPS 730. On the business side you have 4 Vostro, then Optiplex, and Precision workstation. And Optiplex comes in 4 different chassis designs, plus AMD and Intel versions.
I think what we're really seeing here is how the desktop for the home user is becoming more of a niche product for those that MUST have the best performance. In fact most of my customers whom I work on laptops for have told me that they bought their laptop to replace an aging desktop and they really don't want another desktop PC.