In a press release announcing this anniversary edition – a press release that highlights hundreds of thousands of copies sold worldwide and the translation of this game into fourteen languages – Z-Man Games mentions that Pandemic: On the Brink will receive a graphic overhaul as well in 2013 for a new edition. The press release notes that "it will also be possible to purchase a compatibility pack for those of you who would want to play the new edition of On The Brink, but have the previous edition of Pandemic".
In response to my follow-up question, Z-Man's Kalinda Patton says, "In that pack there will be the new role cards, as well as all the cards you find in the original Pandemic with the new design, so people will be able to play with their previous edition of Pandemic with the cards from the new edition."
Finally, a second expansion for the game – Pandemic: In the Lab – will be released in late 2013. The only description from the press release: "In this expansion, you will be transported inside a biotechnology lab in search of a cure. Put your lab coats on and get ready to look for a cure!" (Lab coat not included.)
Update, Jan. 14: In addition to holding a contest on Facebook through February 1, 2013, with a chance for you and a friend to both win a copy of the new edition of Pandemic, Z-Man Games has posted a video of designer Matt Leacock talking about, among other things, the "piles of burning bodies" that might have graced the original cover if he hadn't suggested it was perhaps a bit much.