I said decreased importance, not unimportant. There will always be a need for PCs in development and enterprise, my comment was simply with regard to consumer use.
And I agree there will always be a need for large screen devices, but this doesn't necessarily mean desktops. Smart TVs or set-top boxes like Apple TV or streaming devices like Chromecast or consoles like the Xbox are where the growth is happening in the large format market. The Playstation 3 is the most popular Netflix streaming device.
I'm one of the dinosaurs that uses my laptop for everything these new consumer devices provide, but it doesn't mean I ignore that most people are moving away from this use case.
You can connect a monitor and keyboard to a tablet. Desktop/Other is a dichotomy that didn't age well. My "desktop replacement" is a laptop from 2009, and I expect to replace it with a docking station and something like the Surface in the next few years.
The "decreased importance" you cite is only relative; I for one don't see the desktop becoming unimportant any time soon.
For one thing, my aging parents need 24 inch or bigger screens to adequately see what they're doing. As a programmer and watcher of digital video I need a minimum of 24 inches of 1080p screen.
Then there's the enterprise, where biggish screens are needed for basic IT.