[gentoo-dev] Should there be a preference with qt4 and qt5 USE flags?

[Nikos Chantziaras]

Some ebuilds in portage for Qt-based software support both Qt4 as well 
as Qt5. Some have "+qt4 qt5" in IUSE, others have "qt4 qt5".

Is there a guideline for this somewhere? If a package needs Qt and thus 
lists:

  REQUIRED_USE="^^ ( qt4 qt5 )"

but otherwise doesn't prefer one version over the other and both are 
equally well supported, should qt4 still be enabled by default?