Yes and no. Think of it like release trains; the second edition has left the station, and so isn't being updated directly. It's actually pinned to 1.21; it left the station a while back.
Work on the "2018 edition", which is the next version after "second edition", is just starting. It will be getting updates as new stuff lands, though there may be a bit of lag. In general, docs are going to be a bit weird up to the Rust 2018 release; it's all coming together, but slower at first, faster at the end.
(This means that, as of right this moment, there aren't great docs for impl Trait. I'm working on them right now.)
Work on the "2018 edition", which is the next version after "second edition", is just starting. It will be getting updates as new stuff lands, though there may be a bit of lag. In general, docs are going to be a bit weird up to the Rust 2018 release; it's all coming together, but slower at first, faster at the end.
(This means that, as of right this moment, there aren't great docs for impl Trait. I'm working on them right now.)