Donatas, you are probably underestimating the size of GNOME: there's a lot of modules in extras, though it doesn't use plural forms in extra modules as much as it does in main modules.
As for OpenOffice.org and Firefox, I am pretty sure you don't have to worry about them because they use an advanced translation format and infrastructure which doesn't support concept of plural forms.
Donatas, you are probably underestimating the size of GNOME: there's a lot of modules in extras, though it doesn't use plural forms in extra modules as much as it does in main modules.
As for OpenOffice.org and Firefox, I am pretty sure you don't have to worry about them because they use an advanced translation format and infrastructure which doesn't support concept of plural forms.