I also think that it is better the localizations to be included in the respective third party package. Of course it would be better if there was a way to auto search and install localization packages for the third party apps from the App Manager, otherwise with the current approach we can and up installing tens of non needed localizations with each new installed package.

BTW, such a functionality is expected to be available in Fedora 13 which in some way is related to Meego - so may be someday ...