If that rule has indeed stopped the release of all/most of the post-2005 expansions and musicians feel that this rule doesn't benefit them, then it should be possible for some bigger music labels or individuals, like the composers themselves, to approach this organisation in order to change that. The last option would be if musicians and composers go on a strike, I guess then they will quickly change that. Imagine if all filmmusic composers, music editors etc. won't write/edit any new music for movies until this rule has changed... or do they not care about such releases?