The plan was always to get on stable[1]. Sergio just wasn't willing to compromise on the API to make it happen sooner and I appreciate that since it's a motivation to stabilize the things Rocket depends on. The release notes being discussed here mention that Rocket should be on stable with the next major (Rocket) release.
[1] https://github.com/SergioBenitez/Rocket/issues/19
edit: specify Rocket release, not Rust release