I found out more than a year later, but Mark has passed away in Feb. 2014. It was not unusual to go for long periods without communications between us and I was concerned, but not enough to contact his family directly, and then I found this:
I will keep this website up as long as I am able but I have had no contact with his family and may be forced to shutdown without notice.
It was a pleasure working with him on all his bbotw.com and later Infinity Publishing titles. We never finished his last work or got all his Samurai Cat series back in print and I will always regret that. Mark insisted on high standards and was very firm on how his books were edited and presented. When I was able to publish the older Samurai Cat books, we could not do the interior color pages well enough for sale. The technology to do so became available after I was no longer able to make regular trips to the print shop and we never produced a new edition of the older books. We continued to produce b/w interior books but never produced the full color editions we wanted. I always tried to do the best I could for Mark and I hope it made a positive impact on his life.
Though I was unable to attend his Holiday parties or get together at any conventions for the last half dozen or so, years of his life, I wish that I had been able. I will always remember how great Mark was at telling stories and it was always one of the high points of any meeting with him.
He will be missed,