Just kidding, there are many cool things that are in the works, including Go-style multithreading and effortless automatic differentiation of arbitrary code, allowing you to "machine learn" any algorithm without a complex framework.
But that's all stuff that's not even available in most languages—now is a great time to start using Julia:
1. The latest stable release is 1.1—code you write now will keep working on all 1.x releases
2. There's excellent editor and IDE support for Julia in pretty much every imaginable configuration
3. There's a solid debugger with interfaces from the terminal and IDEs (and I'm sure soon there will be many more)
I think that is worth it for Rust because I think it has good features for building compilers. And really low level runtime-y bits.
Julia has less good features for building compilers.
But still the vast majority of the language is in Julia. Including a lot of the code lowering.
Still, the fact that it's almost all Julia suggests to me it could be all Julia, although maybe that's changed with 1.0+ releases.
Trying to think about why it matters to me, I think what it is a sense that if you can get what Julia offers from another language that does more, it probably is better to use that other language. So I want to see it pushed to be more general-use. Not just for the principle, but because I think in general there are gains to languages in doing so. E.g., my guess is that getting Julia to be self-hosting would require certain efforts that might pay off in other ways, or set the stage for such things.
It's worth noting that this entire effort is done in external packages that work on both Julia 1.0 and 1.1. One of the biggest things Julia previously needed was stability, and we now have that.