Rick,
I didn't know the answer to your question about whether Volumes III and IV would be softback or hardback, so I emailed the publisher, McFarland and Company of Jefferson, North Carolina. They replied that to match the current printing of Volumes I and II in softback, the new Volumes III and IV would also be in softback.

I would guess that a later printing COULD be in hardback, but I don't really know, and I think the publisher does not either, at this time.

Thanks for asking, Bruce Nichols