Most developers I know would still prefer to develop natively for their target platforms. This was the issue when I looked into Qt long ago. Just too many licensing and other headaches no one wanted to deal with for software to be included as part of a commercial release. Even though it was the best cross-platform kit I found at the time (and likely still is). Incidentally, I was proponent of using Qt for the projects I was investigating it for.

I don't think this is going to reduce in any way the number of native Win32 or Mac OS (Carbon or Cocoa) apps we see going forward.