I compiled the slackbuild of qt-5.4.0 and made it work in Porteus. You can download it from here. Libicu51 will be needed to run the qt5 binaries contained there. If you would like to experiment with qml, you will need the qt4-qmlviewer, too.Qt 5 enables highly sophisticated user experiences, offering applications the full capabilities of OpenGL/OpenGL ES graphics acceleration.
In Porteus 3.0.1 KDE4, some xcb libraries and modules are already built in; you will need to install xcb-util-keysyms and xcb-utils-wm only. I made a folder Qt5 in optional and put the necessary modules to work in Qt5.
For other DE's I guess you will have to install all five xcb-modules.