These packages make use of gtk3 useflag which indicates that there are issues of migration to gtk+:3. Gtk3 and similar useflags should be avoided. Adding to tracker. Please have a look.
This package offers an input method for users of many applications. It can build support for qt4, gtk2, and gtk3 toolkits. As per usual Gentoo practice, this is toggled by useflags in this package. There is no reason at this point to deprecate either one of gtk2 or gtk3. Until such time that gtk+:2 will be masked for removal from the tree, there is nothing to be done here. Therefore closing as invalid.