There haven't been any serious proposals yet, but some ideas have been floating around from time to time. For example this blog post has some ideas that might allow them https://smallcultfollowing.com/babysteps/blog/2024/03/04/bor...

The hardest problems I think is that this requires a fundamental change to the language that something might be already borrowed just by existing. It also likely needs to introduce a notion of "stable" places that will not move when you move a prefix of them, e.g. to allow moving a `Box` holding self-referential data. In other words, there's a lot of bikeshedding to do.