There appear to be ample registrations to publish a fourth volume, and perhaps soon a fifth (exact numbers will require substantial additional research).
The challenge to such publication is that many of the unpublished registrations do not include an emblazonement of the arms, and some do not include a full blazon! . Where emblazonments do exist, they are often in black & white. Thus publication will require a substantial amount of research, considerable effort cost to create emblazonments, and in some cases correspondence with the registrant or his heirs. Some registrations may prove impossible to publishin this way.
The current proposal is that Volume IV include 100 registrations, with a bias toward current members, then former members, then non-members. However, the existence of full documentation and an emblazonment will trump this bias.
It is proposed to print the body of this work in house, in full color, with pages 5.5x8.5", and to hire hardcover binding done in small batches. In this way, no great investment will be needed, the work can remain "in print", and corrections may be made as the are discovered.