Mac and Linux ports will be upgraded to Qt 4.8.6 – note that 4.8.6 does NOT compile cleanly from source on OSX; you need at least the -no-phonon and perhaps the -no-webkit options. Fortunately Glade does not need these libraries.
I have yet to try to see if 5.3 is compilable or stable on all platforms (5.1 was definitely not)