I doubt Atlas will answer officially, but hope spring eternal...
As others said Provencal seems the only one missing, and they're doing one per year so it would probably be released in 2014. It then isn't clear whether they'll continue re-making the ones that were already done in prior editions, but my guess is that they will - at the same pace. And the one the fans voted as the most-in-need-of-revision was Rome. I'm guessing Atlas agrees. So my guess is: 2014 Provencal, 2015 Rome, 2016 who-knows.
You might want to check out this thread.
Unfortunately, Atlas keeps future products secret for fairly long...
I thought so too, but now I believe the policy has changed to "we do rgw PDF-thingie we have the time to; probably before the first printing is gone". This thread suggests that still "... but not before a new book is released" is another criterion, and that you should blame Cam Banks for any delays 
I, for one, am waiting eagerly for Tales of Power to reach PDF... I'd settle for Antagonists for now... really..
I, too, am a dedicated fun of Fifth Edition because of its superb writing and production quality. The more I read the core book, the more I appreciate what a work of art it is. And the supplements are consistently good, for years now. This is an amazing achievement for Atlas, made possible by great writers. So I'm just taking this opportunity to say - thanks.