There will be a trade show in Berlin, Germany in September which is comparable to CES. The IFA (Internationale Funkausstellung) might be a platform for Sennheiser to announce new products.
I guess there will be a midrange line using the ring radiator sooner or later. I cannot see any point in pissing off the early buyers of a flagship product like the HD800 by announcing a successor or a superior model so soon.
If driver and construction of the HD800 are what Sennheiser told us, it would be tough to do better. If they are not - well, then they fooled us all.
Having owned the HE60 for quite a while I feel the HD800 more than matches its sonic qualities. It's sort of HE60 plus decent bass, resolution being on par, but that might be attributed to my old ears.
The HE90 was demonstrated side by side with the HD800 by Sennheiser at the highend trade show in Munich, Germany. Maybe some of its magic can be attributed to the price tag and to the fact that it is not available anymore.
I do not believe they will take the stat route once more. While this is ok to make a statement, it does not make too much sense if they want to use the technology in a wide range of products. And this is what their new driver can easily be used for.