Nikon and Atomos have announced 
a few days ago that the new Z6/Z7 cameras will be able to output RAW over HDMI in the future. Atomos will be able to record this signal as ProRes RAW with the Ninja V among others.
Jeromy from Atomos has now mentioned more details in a video interview with Newsshooter, as well as some interesting hints. So he says that not only Nikon is very impressed by the RAW output idea, but also some other ("a few") manufacturers will actively pursue the idea. His statements allow the interpretation that Panasonic, as another manufacturer, is planning a RAW edition for their own cameras, which we've heard for some time now (www.slashcam.de/artikel/Editorials/Bringt-2019-RAW-fuer-alle-.html). He is confident that if Nikon and Panasonic implement RAW via HDMI, Sony and Canon will follow suit. He explicitly points out that an internal RAW recording is also a real option for Nikon.
But back to the technical side: The whole project is still a little "proof-of-concept". Currently the Nikon sends 12 bit linear data via HDMI, which can even be read with more than 4K resolution. Nikon has not yet decided whether a final version of the HDMI 12 bit log will be available. Only 12 Bit Log would allow more than 12 f-stops, if the sensor can sample internally at high frame rates with 14 or 16 Bit linearly.
It is also not yet clear in which frame rates at which resolutions the whole thing will be output by Nikon in the final version. According to Jeromy, 60 fps and higher resolutions will also be possible from Atomo's side, since the uncompressed transmission of Bayer data naturally requires much less bandwidth than 4:2:2 or 4:4:4 signals. According to Jeromy, 16-bit recording will also become possible as soon as a camera can provide such a signal.
On the availability of the solution: Atomos plans to offer a finished version for the Ninja V-Recoder as early as NAB 2019 in April or shortly thereafter. However, Jeromy expects Nikon to provide a firmware update for the Nikon Z-Series in the second half of the year. Until then, the "few" other camera manufacturers will surely also have taken the floor.
;)