If most Rust libs migrate to use index based memory references, then what is the point of the borrow checker ? It would be demoted to a rarely used 1% feature leveraged only by Language Complexity Fanatics - might as well remove it from the language and speed up the slow Rust compile times by orders of magnitude.
The growing adoption of handle/index based resource management is also demonstrating that borrow checking is effectively a failure. Most library authors are beginning to move away from borrow checking as it imposes severe limitations on software design and usability and severe increases to cognitive complexity.