Do you think Panasonic will implement 8k video in the upcoming GH6 camera?

No, they won't without moving to APS-C.

My sources propose what we'll get GH Pro line with APS-C and very expensive lenses. Their problem is what management almost destroyed LSI production and LSI team.

And GH will stay with 6K, but HEVC 10bit and may be 12bit.

Will it have a new organic sensor with more dynamic range?

No

What about Sony? Will they release a 8k mirrorless?

Not soon, at least 2 years ahead. Sony has enormous issues with LSI.

What will be the future of Sony Sensors?

Small step by step progress, see Intel.

It seems Nikon is entering the mirrorless full frame game. What to expect?

Expensive premium camera ala DF, from $2000 to 5000.