Sony announced today two new super telephoto primes, the FE 400mm f/4.5 GM OSS and the FE 600mm f/6.3 GM OSS. Both are around 995g, which is really light for this class. Prices are $2,699 for the 400 and $3,699 for the 600, shipping from 15 October.
I don't shoot birds, but for outdoor football the 400 f/4.5 is very interesting compared to the 200-600, which I rented twice and found heavy for a full match handheld. Nikon has had the 600 PF for some time, so this looks like Sony's answer.
I am curious what the bird people here think. Is a light 600 f/6.3 prime the better choice than the zoom for most people, or is zoom flexibility more important? Happy to answer questions.