It seems like recently the path Ubuntu is moving towards is to have code developed with QML and Qt, and that appears to sync with their move to be able to target tablets, phones, TV devices and the desktop. Information on this can be found here:
However, they also seem to be concurrently pushing Quickly/Python as the development platform for the desktop specifically and this relys on Gtk, as can be seen here:
If I want my application to have longterm viability and to be portable across platforms which should I be investing my time in? Will QML/Qt eventually be pushed as the Ubuntu SDK solution and reliance on Gtk be dropped, or will there be a move to broaden development choices by allowing Gtk apps to be written in QML, and allow Gtk to run on tablets and phones?
It would be helpful to know what the future roadmap is so developers don't invest time and resources down a deadend path...