Tony Ortega checked the OT development timeline and came to conclusion that the highest OT level produced by Hubbard is OT VIII.
I came to the same conclusion based on different considerations. OT VIII is based on an LRH book, A History of Man, so I was told. I read the book, it covers the whole track, there is nothing beyond it. Of course, the freezoners can invent their own OT levels, but, seeing that, LRH will be spinning in the grave (or in OT Heaven).