The latest info from 43 Rumors stemming from supposed leaks on the GH5s or “Low Light Version of the GH5” suggest a 10.28MP sensor with up to 240fps Full HD recording capability. There seems to be an out of step rush to deliver this camera compared to previous releases by Panasonic which may or may not end with a product on the specified date of Jan 8th, 2018.
There has been a clear progression of frame rates from Lumix GH cameras from 60p to 96p, 120p and most recently 180fps with the GH5 and G9. However, if the GH5s ships with 240fps we can safely assume that the spec will now be the bare minimum frame rate for a flagship camera in full HD instead of the 120fps most can shoot in high-quality mode. The GH5 suffered from quality degradation above 120fps with aliasing and moire taking a toll. If the new camera can deliver 240fps with the same quality as 120fps then it will be a milestone mirrorless camera.