RC3 or whatever it will be called will be based on the sarge branch. So, indeed, as far as Bulgarian is concerned, you're already complete.
However, if you have fixes to the translations, you should commit them to the sarge branch. Please note, however that no systematic upload of translation-fixed packages are likely to be made, unless Joey decides it. So, your updates will go in the packages only if some other change triggers an upload.
For *very very* nasty errors (such as a bad spelling error which would make every single Bulgarian user laugh loudly), you may request for an update and get a chance that someone takes care of it.
Thank you for your verbose answer. I was basically asking if there will be point when all packages that have changes in translation are uploaded. So there won't be such mass upload.
Specifically for the Bulgarian translation, there aren't any major problems that I'm aware of :-) There were some inconsistencies in the translation of the 2nd level but I have to refresh my experience with debian-installer before complaining about them.
Regards, ogi