The internal translation functions in TinyME 3.0 have changed a bit, complicating the existing translation functionality for WordPress.
This patch adds all strings from TinyMCE's [lang].js and [lang]_dlg.js files in a single wp-langs.php file, so it can be included in the main .pot file and translated by WordPress' standard translation functions (similarly to the other js translations).
The output from this file is added directly into the gzip compressor for TinyMCE, so when TinyMCE initializes, all strings are already translated and loaded.
The only possible drawback is that wp-langs.php will have to be maintained, however the translation strings in TinyMCE don't change much. They may eventually change when a new major version is released and since v 3.0 just came out, it will be at least a year - year and a half before then. (I've also made a small script to check for new/missing strings that can be run after each TinyMCE upgrade in WordPress.)