Atlus announced via the PlayStation blog today that Metal Slug XX is due on US shelves February 23. Currently, they haven't announced any plans to make the game available for download onto the PSP Go.
Metal Slug XX is a remix of 2008's Metal Slug 7. Players can run and gun through the cartoony action game cooperatively over ad-hoc multiplayer or slog through 70 levels of Combat School, the new singleplayer mode. Additionally, there's a seventh playable character named Leona available for download on PlayStation Network (priced at US99 cents).
The game came out in Japan last month.