They need to move fast, and they do it. Otherwise they won't be able to compete. Ubuntu isn't going to use X11 in their handset OS for example. Yes, initially they started with X11/Qt 4.8 and I actually was concerned that it would take them too long to iterate further, but they stipulated their plans to use Wayland and Qt 5 in the future. They just decided to do it sooner, and I think it's great. Lot's of signigicant changes and often - are not ideal for development, since some were planning to work within Qt 4.8 / X11 initially. But everyone had to be ready to switch to Qt 5 as soon as it would be available. So it is now.

This whole X11 -> Wayland switch is disrupting for the whole Linux universe. So you just feel the bump in Jolla's example. You'll feel it on the desktop too. It'd worth the effort though and is much better than lingering with X11 for who knows how long still. I even consider Wayland to be late. It had to come earlier!