The problem with that is that there's no migration path. This kind of thing probably needs to be done from the bottom up, so we need to unify the underlying object systems (QObject and GObject) first, then the platform abstraction layer (QPA and Gdk/Glib) etc..
This would be hard if there were only a technical issue and everybody agreed that this is the direction to go. But that's not the case, so I don't think it's ever going to happen. And just to be clear: that's a Bad Thing in my opinion.