14 years of development and millions of dollars, c'mon, young?
http://en.wikipedia.org/wiki/Windows_CE

All OS develop over time, like Symbian, S60, Symbian^3.
Or Android 1.0, Android 2.2, Android 2.3

It's no excuse WP7 is young, just because it had a name change.

And seriously, multi-core support is no picnic to make. It took years to have everything in Linux thread-safe and support multiple processors.

As the Plan B says, lets give Microsoft a chance to show what it can give, by making two Nokia-WP7 phones for North American market and try to get operators to love them. If it works, sure, make more.

But do not stop Meego development because that is really a way to be really different and (IMHO) the best. Many Android-developers would jump to Meego straight if it would additionally have Dalvik VM.
Nokia should concentrate to get Meego UI and the most important OS applications ready and shining. It wouldn't matter there is not much Qt-apps, if under FOSS or Alien Dalvik we could run thousands of Android-apps.

In my personal opinion Qt+QML = QtQuick is a mess. C++ itself is a mess (compared to Java) but having two syntaxes (C++, QML) and totally new design patterns are a real trouble.
Sure, support QtQuick in Meego, of course, but support Android and Java apps too.