As a longtime tilt-shift and studio monorail view camera user, I love my current 90mm TS-E, which is nearly flawless optically "as is." About the only things that could significantly improve it would be better anti-reflection coatings, independent rotation of tilt and shift functions - as in the current 17mm and 24mm versions, and bigger beefier control and locking knobs. That said, I probably won't rush to replace my current 90mm lens. My old 24mm TS-E is another matter.
There are two TS-E lenses I really want/need for my type of work, at least one of which I will purchase this year: 1) the 17mm f/4.0 and 2) the 24mm f/3.5 version II. Aside from these two, I would love to have a 135mm f/4.0 TS-E for product work, with near macro capabilities. This longer focal length would go a long way to cement the market for Canon among studio shooters who formerly migrated from large format film to medium format digital backs on view and technical cameras because of the availability of larger image circle type view-camera-like "digital" lenses from Schneider and Rodenstock. With the now supposedly soon-to-come very large megapixel full-frame camera arriving this year or next, Canon would have a shot of eating into that professional market with just another very high quality TS-E lens or two. A TS-E lens longer than 90mm would give these shooters a way to reduce perspective distortion in many product images, such as in automotive and other larger object photography, as well as in ordinary table-top set-ups. Anything from 120mm to about 180mm would be great; I just picked 135mm as a practical and well-worn focal length. In fact, a 120 to 180 f/4.0 - or even a variable aperture f/4.0-f/5.6 - TS-E zoom would be amazing. All this aside, I imagine Canon will most likely just produce the more pedestrian choice - 35mm f/2.8 TS-E. Well, there's always hope, isn't there?