According to this PS3F story, Siren Blood Curse will release in Europe this summer is 12 downloadable parts.
The news came from an asset disc from the SCEE PlayStation Day in London yesterday.
There was no mention of Siren at all in the keynote at the event, but the game was playable on the showfloor. Very grainy it looked too.
Apparently Siren sets you "in the Japanese village of Hanuda, where a TV crew from America arrive to research the legend of the 'Vanished Village' where human sacrifice is said to have taken place thirty years ago."
No word on a US release as yet.