Microsoft is being audacious in unifying the tablet and PC operating systems. The changes in Windows 8/Windows 10 is necessary to this end. Windows 7/Vista are painful with a touchscreen. I think we should recognize what Microsoft is trying to do is very daring. I don't see Android trying to reach the desktop (other than through the browser) and I don't see Apple unifying iOS and MacOS.
I won't be surprised if we're all running full-blown Windows on our phones within five years. Processors keep getting smaller, more powerful, and more power efficient. Phones are also getting bigger. By the end of 2016, Intel is supposed to have Skylake matured, which is a 14 nm processor with a system on chip option. By 2020, we'll see Intel going to a 10 nm or even 7 nm. Similar trends are being paralleled with regard to SSDs and RAM.
At the same time, all the major players are trying to make the PC wireless. Intel's Skylake is supposed to move the ball forward on wireless docking. We have a wireless recharging standard already. So by next year, we'll see devices being docked without wires. Once that technology matures, we'll have phones powerful enough to run Windows and MS Office that we can dock without any wires.
The vision of the future that Microsoft envisions is one where we carry around a phone that is powerful enough to be a desktop replacement for most office users. If all you do is word process and check your email, then you can be on the go all the time. Android and iOS should be concerned because Microsoft may be getting into mobile in a very big way should this vision come to pass, and that's why Microsoft is willing to take a risk on Windows 8, Windows 10, and other attempts to bring Windows onto mobile.