Re: I gotta say...
@Robert. My own guess is that WinRT 2.0 will expand scope beyond Metro, adding desktop app capability with always-on multitasking. The intention to fleshing out its role as the new native Windows API. In this scenario WinRT gradually replaces Win32 on x86/x64 and expands capability on ARM. WPF is not a direct analogy as WinRT belongs to the OS group which is less likely to flip than the dev tools group. However your guess as to the future is as good as mine and you may well prove right about Win9/10.
What a lot of people seem to miss about the whole Metro app deal is even if Windows 8 is a great success, Windows 7 will dominate the installed base for several years especially in corporate, education and other major markets. So it is mostly not an option to replace a software product with a Metro app, even if Metro style works for the app. The best we can consider is adding a Metro style option if we can afford do do the extra work. Considering options, developers will also be looking at OS X, iOS, Android, HTML5 and weighing cost benefits.
The only thing that would change the Win7 dominance would be a dramatic change to the way Microsoft deal with updates. Not impossible but there is zero evidence this will happen before Windows 9.
I agree with you on the lack of consistent support for WPF etc. Microsoft has a poor track record for commitment and the situation for desktop Windows apps is a mess, made worse by poor comminication over recent couple fo years. I'm no fan of Objective C but at least Apple has been consistent.