According to MousePlanet:
Late last week, a construction wall appeared around the long-locked exit to the diorama inside Disneyland’s Sleeping Beauty Castle. Imagineers and construction workers were spotted entering and exiting the space, which was closed nearly seven years ago due to post-9/11 terrorist fears.
While the on-site Imagineers remained mum, some construction workers revealed that the work is to restore the Sleeping Beauty Walkthrough.
No official word on WHEN it will reopen, However rumors from Fantasyland Management and WDI that it should reopen by Christmas OR Early 2009. I did find out that is will still have NO ADA access.
More information is available at the link.