The event announcement says that both Final Fantasy XIII (as a franchise unto itself, not just the eponymous iteration) and Final Fantasy XIV will be at the show, though it doesn't detail if hands-on time with either will be available, or how much new info to expect, unfortunately. Finally, Batman: Arkham Asylum and Mini Ninjas will be descending from Eidos' camp. Gamescom 2009 kicks off on August 19 - 23 in Cologne, Germany.
(Also, Pony Friends 2 ... finally!)