It sounds like a interesting lens, Since its a development announcement. I wonder why they are showing images? A lot can happen during a development process, a lens has to be producible, and the end result may be a lot different from hand made prototypes that are as perfect optically as the lens can get.
I'm sure many with a 100-400L will be watching, my Tamron 200-400 was pretty bad compared to my 100-400L, I sold it off pretty quickly.
It is coming in Spring 2014. I should have a pre-release copy in hand early 2014 and will be sharing as much info as I'm allowed at this point. My contact in the company says that even full resolution shots are looking very impressive from it so far. I'm certainly interested in the lens.