In a recent interview with Dpreview Sony said this:
Think about 8K video. To get that sort of resolution on a sensor, you need larger sensors, otherwise pixel sizes are too small. To get 8K from a micro four thirds sensor, for example, the sizes of the pixels have to be very small, around 2.3 microns. I think larger sensors are important to maintain image quality as we go to higher resolution video and stills.
So either Panasonic and Olympus will stop increasing Megapixels or they will have to find new ways to keep the Pixel size big (Foveon?). But I am pretty sure Panasonic and Olympus will increase the Megapixels. Also because Panasonic stated that they will make an 8K GH camera by 2020. And that would require a 33MP sensor.