This is all over the web, at Cinescopophilia, Vincent Laforet’s blog and Cinema 5D among others. And Cinescopophilia has more on the F55 and F5. They have identical bodies and 4K senrors, but the F5 is going up against the Canon C500 with 1080p/2k recording up to 120FPS (as a free upgrade, it ships at 60FPS) or 120FPS to an outboard recorder for the F5 and internally for the F55, and even do 1080p or 2K at 240 FPS internally. Wow!
These use XAVC, which is 4:2:2 10 Bit at 100Mbps to 300Mbps for 4K. Exciting, though they haven’t priced the cameras as of yet.