They also signed i believe Kate Blanchett, Andy Serkis, Elijah Wood.
Not sure about Christopher Lee or Hugo weaving, but i do know that Orlando bloom is a holdout but they are hopeful they can convince him to sign.
This along with Jackson as writer and director and producer of Both films, They have Howard Shore back for the music. Which will undoubtedly be done at abbey road studios with the London philharmonic.
They only snag i see, no confirmation of Andrew Laszlo as cinematographer, and they are shooting on red digital 3-D instead of super 35.