Any idea on when Qt4.6 will go stable ?
Not before it is actually released. It's still beta!
There's 4.5.3 waiting in updates-testing, but we still have at least one bad
regression we'd like to try to sort out before pushing it to stable (if you
set "three stars echo" for passwords in the KDE settings, the password line
edits lock up; it's not 100% reproducible, but quite often; 4.6 beta appears
to have the same issue).