One concern I've always had with
!Moveproposals is that in many cases, "immovable" values can —and often must —be moved at some point. For example, a self-referential future may be moved into an executor spawn function before being polled. ThePinmodel handles this quite elegantly.
I don't want to derail the thread, but generally speaking, !Move should be paired with some form of in-place construction. That could be in the form of "placement by return" or something more explicit. In-place construction is a highly-requested feature even for movable structs because of its performance benefits. But with !Move, such a feature would be necessary in order to construct things that should never move at all. This should also generally be sufficient for futures.
(Or if in-place Future construction isn't enough and you really need to move them, then the design could be combined with the recent "async is IntoFuture, not Future" proposal: the IntoFuture object could be movable while the Future object is not. Admittedly, backwards compatibility would make this way, way more complicated. Broadly speaking, backwards compatibility with the existing async ecosystem is the hardest part of any !Move proposal; I'd like to believe it's solvable, but it won't be pretty.)