Revealed via the ESRB website. It looks like another set of arcade ports are heading their way to the PS2/PSP. This one is actually rated Mature, as it includes the game Search and Rescue. It looks like at least one Metal Slug title is included here as well.
http://www.esrb.org/ratings/synopsis.jsp?Certificate=28009
http://www.esrb.org/ratings/synopsis.jsp?Certificate=28009