Siliconera and Gematsu's translations, it's an enhanced remake of the 2007 real-time tactics PS3 and Xbox 360 game. As returning producer Akihiro Suzuki said in Famitsu, Koei's "looking to expand upon the foundation of the original game, but we also intend to introduce a load of new elements into the game."
It's one of those "...wha?" announcements that means Koei Tecmo can get away with holding back platforms and release details for now. So even if a Western release is on the cards, we probably won't hear about it for a while.