I hope we can replace the libsyntax parser with one generated from a CFG, with additional disambiguation rules on top, especially if we can easily make that incremental.
It could overlap or conflict with libsyntax2 plans. RLS would likely benefit from it, and could feed back information into it, about the delta from the last successful parse (improving error recovery).
We weren’t even planning to work on a Rust grammar for a longer while! But there seems to be some interest, and the benefits appear almost too good to be true.
We’ll have to see if performance is competitive with the hand-written parser, especially with the cost of additional features for error reporting and recovery.
I expect you’ll hear more within the coming months, especially after the Rust 2018 edition release.