Rosetta sites are the language-specific subdomains of WP.org: ja.wordpress.org, de.wordpress.org, es.wordpress.org, etc.
They offer nice tools (feedback form, showcase, soon a local forum, and oh, A BLOG!), and until recently was used by translators to build local packages.
Some local communities use it as their main (or only) site, while others only rely on it for hosting the WordPress zip archives.
It would be nice to have a conversation about local and international plans from the WordPress project towards communities, in light of the recent evolution and proposed changes for Rosetta sites.
For instance, would long-standing local forums be required to move from their installation to the Rosetta bbPress install? What about their existing showcase? Is there a plan to allow more customization for these sites, such as custom themes, known and secure plugins? Etc.