While Pebble never promised to support languages other than English, I have seen quite a few inquiries here and elsewhere about whether Pebble could support non-Latin characters in the future. I think the Pebble team promised to look into it, but they've got a lot on their plate so I don't expect that to happen soon.
However, I had a thought on a possible stop-gap measure that might even be the best solution we'll get.
Many of us are using Pebble Notifier (or Augmented Smartwatch or Light Flow) to pass some or all notifications to our watch. Would it be possible for the program to include a table of characters that it automatically transliterated into the Latin alphabet?
For example, the Cyrillic (Russian) character "П" would show up on the watch as "P", "Я" as "Ya" and so on.
I'm not a programmer (I knew Basic and Pascal in my youth, HTML and PHP more recently. Obviously not helpful here!) but I would gladly provide a transliteration table for the Cyrillic alphabet and I'm sure we could find volunteers for other languages.