It's been in the rumor mill about 2 years now. Supposedly patents filed, et all, Been there done that. Nikon has a huge hole with their TS line up. Especially if you are working with a D610, D800.
Love it, Canon has a state of the art 17mm and 24mm ( I have the 24mm and have used the 17mm), with sensor technology that is close to 4 years old now. I know, lots of great shots are still being taken with that technology. And Nikon has a huge sensor, great DR and pretty much terrible TS lenses. I know, some folks love the current 24mm and take great shots with it. Just didn't work for me having seen what the Canon can do, (now on the IQ250 at 50MP).
Oh well.
Paul