An administrator from Atari's official forums says that demo version for Alone in the Dark is planned for XboX 360 and PC, and should be out in the first weeks of May.
He also confirmed that Atari will try to release a PS3 demo on the same date, whereas the full version is scheduled for June 2008.
Although it’s coming from the Atari forums, you should take this with a pinch of salt because Atari still didn’t publish an official statement.
You can view the discussion on Atari forums here.