I'll give shortest odds on Senns new BIG THING being a surround sound headphone. They've just cracked into wireless IEMs and full size noise cancelling headphones. So its the only other market segment in which there is mainstream interest and more importantly, growth, where they haven't got a product competing.
I bet it won't be like the Surrounder and as a consequence, will probably suck as much balls as the Zalman 5.1