The Panasonic LUMIX GH5 was announced yesterday for release in early 2017.
http://www.panasonic.com/global/consumer/lumix/gh5.html
4k 50p/60p
4:2:2 10-bit in-camera
Looks like no 6K other than in "6K PHOTO" mode
New body design which will almost certainly mean it won't fit GH4 housings
No mention of the new 5-axis Dual I.S. 2 IBIS that's in the G80/G81/G85. Would seem strange not to include it in the flagship camera.
I may get it, chiefly for the 60p @ 4k. I really hope the auto-focus and underwater colour rendition are improved, as these are my 2 biggest issues with the GH4 for underwater use.