For details on what you're looking at, and on the basic gameplay. see this story.
Kokuga was featured during G.Rev's webcast earlier today (the same program that saw the announcement of Senko no Ronde for Vita). During the Kokuga segment, CEO Hiroyuki Maruyama said that the game was originally in planning for DS. He also revealed that while the four player game sharing mode is meant to be cooperative, you can attack your friends' ships.
Regarding release date, Maruyama said that Spring will be difficult, so it will probably be Summer.
source | andriasang
That announcement is targeted to Japan, other regions are unknown as of yet.