Encontrei o seguinte em seu site , mas não tenho uma data para acompanhar este comentário . Ele também se refere ao seu "último romance, THE DEPTHS OF TIME foi publicado no final de fevereiro de 2000", por isso pode não estar muito atualizado.
I receive many queries, asking if I plan to do any further work in the series of books started with THE RING OF CHARON and THE SHATTERED SPHERE. The answer is yes -- but not just yet. I have not decide when I will write the next one, but I definitely will write it. I have always intended to write an open-ended series of book in this universe. I plan to call the next one THE FALLING WORLD. I looked over my notes for that book a while back, and I must admit reading them made me want to get started on it soon. However -- I do have other books I want to write as well. Sooner or later, I will juggle my time enough to let me make a start on THE FALLING WORLD. I'll keep you posted.