WW Norton & Company, Inc. is the publisher of The History of the ___ World series.
While there are general plans for future volumes to complete the series, you may be able to help the process by contacting WW Norton directly to ask when they plan to publish the next volume of HOTW. Customer interest influences publishing decisions.
WW Norton has made the audiobooks available on Audible.
When we have further information, we will update this FAQ.