Unless Canonical hired a whole bunch of devs away from Microsoft or Apple, I don't see this ending well. The move to QT is a good one, they should have done that from the beginning though. Mir? Reminds me of the space station. Not a good omen.
But what's even worse for Canonical is this: Ubuntu is not stable. I've had a ton of issues with both 12.04 and 12.10, and I have fairly standard hardware, and don't mess with things. They have no vendors for their smartphone and tablet OS yet. They have no major vendor for the desktop OS.
I'm typing this on openSUSE 12.3 right now. KDE 4.10 is great, and SUSE 12.3 is great. Fast and stable (on my Thinkpad). And it's not officially released yet. But already giving me less trouble than Ubuntu.
I'm afraid Ubuntu will more than likely underwhelm on every platform, if I were to place a wager that anything could rival Apple and MS, it would be that no desktop Linux will truly rival them, and the only mobile Linux operating system with a shot at the iOS/Android duopoly is Sailfish by Jolla. Desktop Linux is nothing more than a developer platform these days (and maybe a niche gaming OS in the future), and I think that will become more apparent as time goes by...