Look around on imdb or horror websites, such as bloodydisgusting. There are numberous story articles on imdb alone.
Wes Craven is undecided since his last involvement with Dimension/TWC wasn't a pleasent one (Cursed). And no one knows about Neve, as she had a limited pressense in Scream 3.
But it is scheduled for a 2010 release.
There was also an interesting story about how the Weinsteins signed a 80 movie exclusive deal with Showtime, that the next 80 films to come out through the Weinsteins would be preimiered on Showtime first. Included were a RoboCop remake, I believe the Pirahna remake (not sure), and Scream 4.
Edit- Here are some 'exclusive facts' (Bloodydisgusting)
Kevin Williamson is writing a draft for the film, Wes Craven may or may not direct, but is likely to, they are making offers to the Arquettes and Campbell for cameos, and it will be a 'younger version' of the Scream movies.
They kinda did already.
It was called Scream 4: The Final Scream
Funding fell through, and they ended up with a cruddy movie that went straight to video simply called "Final Stab"
This is technically Scream 4.
However, they are doing a new movie that will bear the official title Scream 4 now, and it is set to come to theaters next year. Williamson is writing and Wes Craven is slated to direct. Casting hasn't started yet, so no word on who will be in it.