A great link. I suggest that others read the Callow interview graciously supplied by KeithDA.No - I still think only 4 volumes are planned..
http://www.wellesnet.com/simon-callow-talks-about-orson-welles-volume-3-one-man-band/
As the third one, 'One man band' covers 'Chimes' - I suggest people don't hold off waiting for all 4 to be available. Volumes 1 (including Citizen Kane) and 3 are the most readable....
If 3-4 volumes of Welles by Callow didn't yet whet one's appetite, then this interview will close the deal for any and all.