Although it hasn't been 100% confirmed, USA Today is reporting that Anna Paquin and Kristen Bell are set to film cameos in the upcoming Scream 4. There's no info on what parts they'll play, but the news is more than feasible.
The franchise is well known for its female celebrity cameos during the opening scenes of the film - most famously Drew Barrymore at the beginning of the first one - and a casting call that went out a few months ago included several smaller roles where they were specifically looking for someone with a recognisable face. It wouldn't be surprising therefore if either Paquin, Bell or both get sliced and diced before the credits even roll!
It's also rumoured that Paquin and Bell won't be the only famous faces to show up for cameo roles, with Wes Craven planning plenty more. However he's trying to keep them under his hat, so everything comes as a surprise when the movie opens next April.