Hi John Masters,
All I know is that Ray Rimell plans to do a volume 4 someday, but it's certainly not in the immediate future. He has several other projects in line to do first.
Next in line, as far as I know, is a volume devoted to the REAL Nieuports flown by Escadrille N.124, the "Lafayette Escadrille". It has been authored by the always readable Jon Guttman, with lots of input from the master, Alan Toelle. Obviously, it is designed to coincide with the release of 'Flyboys' and should give modelers lots of real, accurate info about the actual Nieuports flown by this famous unit. And, yes, it will have a good deal of new material that was not featured in Jon's Osprey book on the Lafayette. I think it will be available (hopefully) about the time "Flyboys" opens.
Next is a little book on Fokker Dr.I Jasta markings by some no-account idiot.
I don't know when D.VII Anthology 4 will be produced, but I'm confident that Ray will bring it out someday (maybe in 2007?). I believe it will concentrate on post-war uses and color schemes of the D.VII as flown by a multitude of nations. My contribution, if any, will be limited to corrections

and addenda to my earlier contributions.
Greg VanWyngarden