Aside from the usual bonuses of epic oppai-engine you'll be getting a "Girls Visual File Book", A Soundtrack CD and an Audio Drama CD. The only thing missing now is the game's official release of a game play clip to see how the new Senran Kagura compares to it's prequel. Lastly the only thing that the game needs is an anime adaption which will infuriates the sleeping otaku blood and an English version of the game. Will it be included in the Winter Lineup? Who Knows!
Before I forget, you can go here to the official website which offers the bonus items. It will give you more details of the game and the items.