I think there's nothing to fear. The announcement states that in most cases you should be able to port your applications from Qt4 into Qt5 with little or no modifications. On the other hand, I was an skeptic in regards to QML at first, but after using it I fell in love with it. It's logical and very easy to learn, and having similarities with web development means expanding the availabilty of programmers and designers who can work immediately in your project. Great stuff.