Any plans to drop the desktop UI do appear to be on hold. Changes introduced in 8.1 and proposed changes would seem to indicate the desktop mode won't be going away soon. Frankly most people would not notice the performance difference but they are bothered if the GUI changes radically.
If MS did abandon the desktop in favour of Metro it would be commercial suicide. Enterprise would consider alternatives.
I think with enough work the MUI could replace the desktop its in a early stage at the moment if anything M$ is just taking there time getting user use to the MUI over multiple OS releases each one adding more function tot he MUI. It just takes time how long did it take most user to switch tot he desktop when they released it instead of command line?
So you want us all to upgrade to Windows 8 because it's boots faster. Just throw out all other factors normally used when comparing operating systems to each other and go with Windows 8 because it boots faster? *click....click....click....KABOOM!!!!!!*
Your second paragraph contains even more bizarre statements than the first. Nothing is stopping Microsoft from competing in the tablets/phones market. But I do agree with part of a statement you made:
"conforming your mobile centric OS to desktop users makes less sense to me."
Conforming either one to the other makes absolutely no sense at all. Why would I want to use a tablet OS on a desktop as you yourself stated that Windows 8 is - a "mobile centric OS"? Why would mobile users want to carry a keyboard/mouse in a gun holster on their hip and a laser printer on their back. So they can look like a modern day ghostbuster who really knows his tech stuff? Uh...I don't think so. If we cant ever get over the fact that mobile devices and desktop devices are "not the same thing" there will never be a solution. You can't solve a problem if you don't understand the problem.
"The further generations were going to drop the desktop all together and run everything through the MUI."
Dumbest statement of your entire post. The definition of desktop needs to be made clear here. It no longer most accurately represents the "size" of the device we are talking about. But what we "do" with that device. The "desktop" will not be going away ever because it represents a virtual place where people go to get serious work done.
When people can spend 8 hours a day editing movies, building websites, entering hundreds of medical/dental records, writing a book, or building the next "Call of Duty" engine on a tablet without a keyboard and a mouse - only using "chimpanzee-like" swipes - then that is the day the desktop will be going away. If you believe for a second that that day is arriving anytime soon, you are living on a planet which I have not yet heard of.
The desktop was kept in Windows 8 operating system because without it nothing could be produced for all you tablet consuming chimps to feast on day after day after day. The day the desktop dies your tablet dies with it.
Well the Speed comments were a discussion between me and tipstir, should you move to windows 8 because it boots fast? Depends on what your moving from and if you have never heard of putting the computer to sleep. On to the rest of the comment... Can you edit movies on a touch screen sure can I have seen plenty of people do it, did on my tablet the other day in a pinch because my desktop was down, wasn't any trouble. Do I see professional video editing moving to tablets no, never stated that. Do I see tabelts having medical records entered into them? all the time every doctor at my local hospital has a tabelt with them at all times, so there already heavily in that field. Your talking specialized fields that make up less then 10% of computer sales anymore, in the beginning of computing Business/enterprise was where companies like MS focused because that's where the money was, consumers now drive the field more then business does. Your average consumer will go through 4 computers and 3 OS's before a business goes through one of each. They are the majority business's tend to move toward the majority if I am correct? Will Microsoft abandon enterprises? prob not they will deliver what those customers need, when you say business that's what I think of, those are the business money makers for MS, small business is a tiny chunk of MS's profit pie anymore.
Microsft is moving away form the desktop, not a statement by me just common sense really, the majority of computer sales will be on tablets and phone with in the next 5 years, desktops are terrible on the touch screen. Is MUI a replacement for a desktop yet? HECK NO!!! MUI is in its infancy (less then 1 year old) the desktop sucked back in windows 3.1 if I remember correctly, but evolved over time into the system that we have today. MUI is doing the same thing, computing hardware is changing (finally) and its going mobile. With enough work MUI would be a desktop replacement to any user while still functioning great for users on the go. ATM there focusing mobile, a lot of the speculated "threshold" features are adding more desktop functions to MUI. As for tablets doing everything a desktop can do, well they can, tablets if anything have shown how flexible they can be, mobile when you need them to be, but add a dock (keyboard or station) and your right back to a "desktop" work environment and with how hard Intel and AMD (not to mentions ARM's advancement) are pushing there low power development there's gonna be plenty of power behind these devices still.
For the needs you bring up and for your personnel needs MUI doesn't fit them atm (though some of those needs are being met for others in those industry fields). That's why Windows 7 is still here and is supported for the next 5 years +. Keep using what works and watch what the markets shifts into. If MS continues on the course for MUI and keeps adding features they have talked about and features I can see they have set the foundations for already (though no word on whether they are coming or not) the MUI might impress you in 5-6 years from now (maybe sooner) and you can move to that system. But its young and just entering the market, I wouldn't say your kid is way worse at math then you and expect that at 1 year old to be as good as you , not when you have had all those years to develop your skills
In the end I live on planet earth (same as you I presume) as I said computing is changing MS is just trying to keep up, while not cracking to many egg shells on the way, when you try and plz everybody you will always fail.