Are .ui files supposed to be compatible between Qt4 and Qt5?

Code generated by uic for Qt5 from a .ui file created with Designer for Qt4 may not compile because of the removal of the deprecated QLCDNumber::numDigits property. If it is intended that .ui files are not portable between Qt4 and Qt5 then the version number of .ui files should be increased to 5.0. If they should be portable then the numDigits property should be restored to Qt5 (but still marked as deprecated). I don't know if there are other similar deprecated properties.