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.