If you start the software Pinnacle Game Profiler on your PC, the commands contained in pinnacle.exe will be executed on your PC. Our experience with QML over the last years has shown us that it is the superior technology for building UIs in the long term. The pinnacle.exe is an executable file on your computer's hard drive. And QML/Qt Quick was the answer we came up with to solve this problem. This implies that we needed to do something new here. And they are simply not implementable using the QWidget infrastructure.
The fluid animated user interfaces that are already there on Devices such as smartphones and tablets are now also starting to appear also on desktops. Adding support for the kind of animations used in these user interfaces is extremely difficult using QWidgets, as they were designed for the mostly static user interfaces that predominated until a couple of years ago.
New user interfaces such as the Windows 8 Metro UI are not things we could simply add to our existing QWidget infrastructure. I personally believe that over time we will see more and more apps being written that way, as I believe it is the better solution in the long term. What we did with Qt 5 is to add a new way to do applications with QML. But this can change any day if someone has some interest or need to do more active development in this area. Yes, the Qt Widgets module we have in Qt 5 is right now marked as 'done', which means we don't have anybody actively working on new features for the module at this point in time.
And of course this includes QWidget and your application written in C++. We have promised to try to keep as much source compatibility with Qt 4.x as we can. You can continue writing your application in exactly the same way as you have been doing with Qt 4.x. Let me just state it very clearly here: QWidget and all derived classes are a core part of Qt 5 on the Desktop. The post on the Qt 5 alpha was focused on the new things we enable and add with Qt 5. I thought now would be a good time to address some of these concerns in this post. We have seen the many questions and the concerns raised about our commitment to C++ and QWidget in Qt 5.