Sony China tweeted this (google translated):
In response to the ENG 4K market demand, Sony will launch a new product at the show, new imaging devices, new codecs, and new wireless transmissions, all of which are the ultimate in 4K shoulder-shoulders. If you want to get a closer look at this mysterious new product, please come to the Sony booth and have a quick look
The camera will be announced tomorrow (August 21).
The important news are the NEW CODECS. These are rumored to be used on the new A7sIII and maybe on the new A6700 too???