According to BHphoto the new Sony 400mm lens will ship in September 2018
The Japanese site DC.watch posted an interview they had with the Sony GM developers. There is little inof about the future lenses to come. All we got is this:
– There will be no 35mm f/1.4 or 50mm f/1.4 GM version. At leats not for the next 2 years. The reason is that the Zeiss lenses are very new and it makes no sense to overlap specs.
– Sony is working busy on making new GM lenses. And the roadmap is based on the customers need (hint there might be a wide angle GM).
My bet is that in 2018 we will see a wide angle GM prime lens and a 135mm FE f/1.8 GM. And than of course we will get the already announced 400mm f/2.8 FE.