Some answers
Perhaps, I can be of some assistance in understanding a couple of questions or assertions that have been made in this thread.
First of all, Canon does offer both swing or tilt of the lens (front focus plane) on all their TS-E lenses. An analog of view camera tilt is available, defined by the lens plane moving through a defined vertically oriented arc that travels around the horizontal axis traveling through - and in front of and behind - the central, near nodal point of the lens. After rotating the mount 90 degrees, the TS-E lenses can use the exact same controls as were used for the tilt movement to swing the lens plane through a defined horizontally oriented arc that travels from left to right, around the vertical axis going through - and in front of and behind - the central, near nodal point of the lens. And if you choose to rotate the lens mount less than 90 degrees off either the vertical or horizontal axes, you will be able to combine the effects, somewhat, of both a swing and a tilt of the lens plane, the effects depending on the position of the mount.
As to the person who speculated that perhaps Canon was going to make the lens able to swing, as well as tilt, well, the above paragraph explains that that is already possible. However, if the poster is referring to the true capability of a monorail (non-monorails can also do this, but usually only tilt from the bottom, rather than the center) view camera, then, no, no current TS-E lens can achieve that. This is because, besides being able to swing/tilt the lens plane only, as TS-E lenses do, a monorail view camera can also swing/tilt the image plane (for view camera, it's the film/digital back; for a DSLR it would be the entire camera with sensor, but not lens), independently of whatever one chooses to do with the lens plane. Therefore, the view camera can swing or tilt either the front or back, in whatever direction one chooses, or swing or tilt them both at the same time. The uses of this are quite important. Tilting or swinging the back not only helps to indirectly manipulate the front focus plane much like the camera front does, but it can do something else quite important; it can effect the apparent distortion of the subject, from rectilinear-looking to comical levels of "distortion," stretching or compressing the subject to either "correct" its look or purposefully make it look less realistic. Then, oftentimes, the front is counter-moved to reset the focus plane to make up for the change of the image plane, so that the so-called Scheimpflug effect can still bring about relatively sharp focus.
Given the above, Canon could actually make a lens with two tilt/shift mechanisms, one in the "normal" position to allow front lens plane manipulation and one at the base of the lens to simulate rear standard image plane manipulation. The lens would be horribly complicated to make, and the glass itself would have to deliver a truly massively larger image circle than normal "full-frame" lenses, or even existing TS-E lenses, to compensate for the possible off-angle light projection of the two different standards. But, this could be done, especially so with a lens longer than 90 mm. I doubt if Canon, or any other lens maker will ever actually do such a thing, but it would be possible.
And as to whether having a super-telephoto-like lens mount adapter on a TS-E lens would make multiple exposure panorama-making easier, by not affecting the perspective of the multiple shifted exposures, the answer is: I think so. One TS-E's shifted lens view's perspective will not exactly match the perspective of a view from an image shifted along the same axis by the same lens, unless an appropriate image plane shift could mitigate it. To do this properly, it would work best if only the camera-sensor back itself were shifted through the image plane, and, when the lens itself is immobile on a tripod, the lens movements themselves actually serve to move only the camera body through the immobile image plane. If this does not seem practical for the owners of existing TS-E lenses to achieve, it is good to know that it is not always necessary, given the "fudge factors" available in post-processing, and that it is still possible to achieve with some extra effort and cost, via various adapters and rails.
I hope this helps.
David
. Beyond that, maybe the T/S mechanisms will improved beyond the current TS-E Ls, with more durable parts.
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