Good news, although not for my wallet. The 45 & 90mm update is long overdue.
As for a 200mm T/S - what would be the use case for that?
Landscapes.
Getting the entire scene in focus is always a challenge at longer focal lengths. And, with increasing sensor resolution, you can't just stop down to f/16 or f/22 if you want to retain fine detail and microcontrast. Tilt is a good option for getting around that.
Long tilt-shifts can also be good for creative group portraits, as they allow you to arrange subjects such that the line or plane formed by the subjects' faces do not have to be parallel to the sensor plane, while retaining sharp focus on all of them.
Generally, as focal length increases, shift becomes less useful (less geometrical distortion to correct when fixing verticals or stitching panoramas, so there's less lost when using a normal lens compared with at shorter focal lengths) but tilt becomes much more useful. A camera with a tiltable sensor would be ideal, but, since Canon is unlikely to introduce that any time soon, a long tilt-shift would be the next-best thing.
I also hope these lenses come with an inbuilt tripod foot, like the Schneider tilt-shifts - it would make them even better for stitching, without having to turn to third-party solutions.