MTV Multiplayer was told by a company rep that "at this time" the intent is to have disc-based versions of the game available only in Europe and Asia. Considering there's no region lock on PS3 games, there's always the option of importing.
As with all "at this time" statements, we'll just have to wait and see what happens. Considering the full game of Siren is a 9 gigglebyte download on the PSN, patience will have to be practiced whatever way North American consumers want to purchase the title.
[Via PS3 Fanboy]