I meant to make this comment on the last news post about the GH5 but didn't get around to it...
I want to throw some water(?) on the idea that Panasonic will include the GX80/85 IBIS on the GH5. I think there's a lot of potential for disappointment if you expect this. I can't think of any camera right now with a large sensor, 4k, and IBIS that doesn't come with a recording time limit, and often with overheating issues even before reaching that time limit. The reason, from what I understand, is that as soon as you introduce IBIS you can no longer attach the sensor to a large enough heat sink because it would be too difficult (impossible?) to move the whole combination as is required with IBIS. Realize that IBIS would also limit their ability to produce high frame rates, for the same reason (sensor overheating). The GX80/85 has that great IBIS but also has a max frame rate of 60P and a max recording time of 30 minutes.
Engineering involves balancing many factors. Unless Panasonic has come up with some engineering breakthrough that would allow a combination of large sensor, 4k, IBIS, high frame rates, and no time limits (which I think is a very unlikely combination), I, for one, would choose unlimited record times over both IBIS and high frame rates. I think that unlimited recording time is one of the really special features of the GH4, and one of the main factors that would make me choose it over any of the competitors. If they do away with that, it would open up a lot of (competitor) options for me.
Oh, one more thing... I haven't yet seen any good reasons for them to change the body design from the GH3&GH4 -> GH5. Hopefully Panasonic realizes that they would do better to build on top of what they already have, rather than start from scratch and obsolete a lot of accessories.