Tantacrul, (I think) the lead of the Audacity (and also the guys that lead Muse Score) said that V4 is migrating everything first to QT. After that, they will start adding more features and also fix more backwards compatibility to the old engine (because V4 will also introduce new engine)
You could have just asked the developers! Or looked at the roadmap. Lazy journalism at its finest.
Tantacrul, (I think) the lead of the Audacity (and also the guys that lead Muse Score) said that V4 is migrating everything first to QT. After that, they will start adding more features and also fix more backwards compatibility to the old engine (because V4 will also introduce new engine)