Visual application development tools for Linux/ Windows (KDE4) ?

[Linuxguy123]

I need to develop a small multi platform (ie Windows and Linux)
application.  Normally I would do this sort of thing using Java with the
Eclipse Visual Editor tool. 

I hear rumblings that KDE4 is going to run on Windows.  How long will it
be before we can run real/significant QT apps on Windows ?   

I see that F10 has QT3 Designer in the offerings, but I don't see a QT4
Designer.  Why is that ?

What other multi platform development options are there ?

Thanks.