I've seen it stated a few times that after Rust 1.0 there will be no more backwards compatible changes.
Does that mean ever, or just that it'll be stable for some time before people start considering a 2.0 to try and fix whatever warts are discovered from wider usage of 1.0+ ?
It certainly doesn't necessarily mean ever. Who even knows who will be leading the project ten years from now! But it does mean that it will be quite a while before the hypothetical 2.0 where we could consider breaking backwards compatibility. How long "quite a while" will turn out to be, I can't say. But it will certainly be an improvement over the current situation, where the language breaks about once a week. :)
Does that mean ever, or just that it'll be stable for some time before people start considering a 2.0 to try and fix whatever warts are discovered from wider usage of 1.0+ ?