If the part about how "most of those crates wouldn't be doing funny operations on pointers" can be verified automatically in a way that preserves safety guarantees when usize != uaddr/uptr, these crates can continue to build without transitioning to a newer edition. Otherwise, upgrading these crates is the right move. Other code targeting earlier editions of Rust would still build, they would simply need a compiler version update when depending on the newly-upgraded crates.