According to this ThreeSpeech preview of Siren: Blood Curse, the episodic horror will cost you 600Mb of hard drive per chunk. The game's being split into 12 episodes.
Before you start squealing, though, you're able to delete any episode and re-download it whenever you like. Alternatively you could just buy the English language version on Blu-ray from Japan. The choice is yours.
Game's out this summer in America and Europe. Thanks, PS3F.