The Sony FE 12-24mm f/4 G lens has already released, and currently in stock at Amazon/ B&H Photo/Adorama. Imaging-Resource has reviewed this lens, and said that this is a great ultra-wide zoom lens with superb image quality.
Conclusions from Imaging-Resource:
Image quality when shooting outdoors on the a9 was superb and I wouldn’t hesitate to add the 12-24mm ultra-wide zoom lens to my bag!
The Sony FE 12-24mm f/4 appears to be a very capable lens, and may even rival the quality of the Canon L series glass that many adore. It was certainly a joy with which to shoot, and I’m more than satisfied with the results I obtained.