Delphi is still around, as is the open source clone Lazarus. It's certainly not as popular as it used to be but still actively developed with people using it.
[0] https://github.com/ssebastianj/ia2013-tpi-rl/blob/master/gui...
Going back and forth between Qt Designer and PyDev was (is?) ancient. Unfortunately I couldn't find a way to automate the compilation step (perhaps with a hook from Qt Designer?)