There's a reason I'm not on Windows 8. XD
Trying to force one interface model for all devices is stupid. It's like ceasing to manufacture regular monitors because 3D is currently the "in" thing. Touch is great...for mobile/small devices. Even then, it's only good because the alternatives are not really sensible. On a desktop PC, touch makes no sense. It might have the occasional use for specific applications, but not only is keyboard/mouse more intuitive, it also doesn't get fingerprints all over your freaking viewable space!
All touch does on a desktop is reduce the amount of things you can interact with because it requires allowances for less precise input. I.e. everything has to be larger and more finger-friendly. The amount of features you lose/can't do as accurately because of a touch interface is absurd. It's a "one size fits all" mentality and that has been proven to be stupid countless times in the past - it's the "gaming laptop" approach, and while it works, it's never going to be the *right* solution for either of the tasks you're applying it to.
Why Microsoft though this approach was sensible or going to help them in any way is beyond me. More likely developing one OS was more cost-effective in development terms, but that's a short-sighted approach.
And as much as they insist that desktop sales are down, mobile is taking over, etc, etc, I'm still not seeing it. They might take over for everyday use applications, but phones and 12" tablets still are not the best way to view media content, they're not the best way to write things like reports, documentation, code, essays, spreadsheets, or anything else that requires more than five seconds of typing. They're not good for doing side-by-side comparisons or comparing multiple pages of content. They're not good for extended periods of use for most things, even, due to the posture and gestures they force you to assume.
Nor are they suitable for non-mobile gaming. And no matter how much Microsoft wants to think otherwise, no, removing desktops PCs won't make their consoles do better.
Just because something is more convenient in small doses does not make it the better platform by default. It makes it another option to consider. At the end of the day, short of neural-interface futuretech, keyboard will always be the option of choice for bulk data entry applications - which is a rather large percentage of business use, for a start. The same as the precision of a mouse will always make it superior for most gaming applications. Or why a stylus will always be better for drawing on tablets than a finger.
Approaches like this, ones where people try to sell the idea of "death of the desktop", sounds a lot like people heralding e-readers as the end of printed books, or the internet as the death of public libraries. Piracy will destroy the movie industry, etc. Heck, we still use analogue clocks/watches often enough! And the concept which I've read elsewhere that Microsoft is calling 10 the "last major release" sounds like things they've said before. It sounds like a lie. Or the death of Microsoft.
It's oversimplifying their target audience. They made the mistake of broad-base generalisations with the Xbox One and Windows 8...hopefully Win10 learns from that mistake. *sigh*
....and yes, that turned into much more of a rant about semi-tangential issues than I had intended, lol.