The titles of most movies tend to get lost in translation to non-english territories (some of them are hillarious) so even if the movie's title in the UK and US etc is Angels and Demons, its possible that it could be marketed at Illuminati in other territories.
Even if that is true, then the market for this domain is limited on the territories it applies to. Until we have confirmation that the movie will go ahead, and following that, confirmation on its name in various markets etc, then this domain as one based around the movie doesn't have a lot of potential.
HOWEVER
There is a lot of potential for this domain outside of being themed around the new Dan Brown movie - the rise in interest over such groups as the Freemasons, Illuminati, Knights Templar etc which has been fuelled by the furore over Da Vinci Code as well as many other events etc could bolster the development potential of this domain name.
And, if all else fails and the A+D movie is not named Illuminati in any territory, then its not inconceivable that at some point a movie based solely around this society will surface.
I'm not going to take a shot at a value for this because I think theres a lot of variables to consider if you persue the potential A+D movie tie-in. Any other direction you take will depend entirely on how you develop it.
I hope thats at least made some form of sense and has been helpful in some way.
Good luck with the domain.