Koei announced Shin Sangoku Musou 4 Moushouden (Dynasty Warriors 5 Xtreme Legends) for PlayStation 2. The game is scheduled to release in Japan in September, for 4494 yen; the game will feature all new play modes not found in Shin Sangoku Musou 4.
(http://www.the-magicbox.com/gaming.htm)
A wild guess, infinite dungeons mode like in Samurai Warriors?