According to this FM forum post, Carl Zeiss will be releasing a new Distagon 25mm f/2.0 lens this month:
"Yes, I have an idea about the new 25. It will be announced in October, so keep an eye for the Zeiss website. And if everything goes well, delivery of the first production batch will be in Germany right before Christmas."
The current Zeiss Distagon T 25mm lens has a f/2.8 aperture.