During some periods in the development of Debian Installer, the development team may decide to "freeze" the number of supported languages. All languages which start after the freeze date are called prospective languages. These languages won't go in the prepared release but rather in the next release of the installer.
Another reason for keeping a language out of the installer is a too incomplete translation.
Prospective languages are kept in the file
packages/po/PROSPECTIVE along with the master po
files. Translators can continue translating, but the translations will
be kept back and not spread into packages by the synchronisation
script (see Section 6.5, “Translation synchronisation”).
The status of prospective languages can be fetched on the status pages
(Section 6.1, “Translation status pages”) just like every other
language. However, the language is not ranked along with other
languages in the
rank.txt file. A prospective
language is not listed there and graphs are not calculated.