Figured I would throw my speculations out there after reading through the thread.
I know some people have brought up the idea that the EVA1 sensor may be used in this "new GH5". However, a lot of people (myself included) do not think it makes sense that a modified GH5 (or any GH series camera) would have a larger than m43 sized sensor inside it. But, what if Panasonic ends up doing the same thing RED did with the Raven?
RED basically used sensors from the 6K Dragon that did not pass spec over the entire imager - cut them down to 4.5K, and threw them into the Raven. So, rather than "throwing away" sensors that didn't meet QC standards, they cut off the "unusable portions", and put them into a new camera. Basically, they found a way to make money from sensors that couldn't be used!
So with that in mind, what if the "new GH5" does indeed contain the EVA1 sensor - but a m43 cut of it? It would explain the hypothetical better DR, colors, and low light.
Just a guess. Would be pretty awesome if that was the case. Not holding my breath though.