This is complementary to development in SAFE, for sure:
Actually, it has two parts (three if you count future plugins): A back-end written in Rust and a front-end in whatever development language is native to the platform, with plugins written in anything. The interface between the parts is JSON-RPC.
I came across this while looking for an alternative to Sublime Text 3, which is very good in most respects but has some niggling aspects.
I love the stated goals of Xi, which are exactly what I wish for. They will probably be successful although the project is only a few weeks old, so only partly built. The back-end compiles on my Linux machine but there’s nothing to see when it runs, no front-end yet for Linux, and I’ll have to wait for them to publish some more clues.