When Will Metal Slug 4 & 5 Release in SG?

So i have just brought Metal Slug 3 for my PS2, i wonder when will Metal Slug 4 & 5 release in my country call "Singapore" it is located in Asia. So can the admin or the creator of the game tell me pls. I'am a big fan of Metal Slug! ;D And i mean when will Metal Slug 4 & 5 Release in my country for my PS2 console only?? So please tell me the dates if u know, thankz! Reply Soon!