Speaking for myself and not for RIM
With RIM's serious push for Qt as part of the core frameworks and a more Open Source push for its ecosystem, it's the right time for me to jump in.
I Just started my initial porting of the Weather Forecast engine and applet to BlackBerry 10. It won't be Plasma based but pure Qt and Cascades UI with the kinds of effects that I really want to use.
I have to say it's pretty easy to get going. You go here: BlackBerry 10 Development