New blog post by Walter Bright is up:
Ownership and Borrowing. It’s memory efficient, as performant as manual management, and mechanically auditable. It has been recently popularized by the Rust programming language. It has its downsides, too, in the form of a reputation for having to rethink how one composes algorithms and data structures.
While I welcome this addition (assuming it actually materializes) I think that last sentence understates the downsides. In my experience, it's just a lot more taxing to have to think about memory all the time. In terms of developer productivity, you can't beat garbage collection, and things like this are a last resort for the small amount of code that absolutely can't handle garbage collection.