Currently Audacity's dependency is "DEPEND=">=x11-libs/wxGTK-2.6" this will cause an issue because when wxGTK 2.8.0 is added to the tree, see working ebuild: http://bugs.gentoo.org/145884 it will fail to build. I have this development wxGTK ebuild installed of 2.8.0 because I'm testing other software that depends on 2.8 version. Here is the developer reply on the matter, http://audacityteam.org/forum/thread/4055 It might be possible in future versions to build Audacity against wxGTK-2.8.0 but for the moment it is not and therefore this ebuild will break.
Created attachment 112371 [details, diff] audacitywxgtkfix.diff alters the dependency in the ebuild to work correctly with a system including both wxGTK 2.6 and 2.8
deps fixed, thanks for tracking this :)