More importantly, for my niche I don't see anything that can readily replace C++. Rust has very little support for scientific computing. Julia is great, and will replace my high level statistical inference code, but it's not designed to let me design low-level close-to-the-metal data structures. Scala has memory issues, which will be hopefully less problematic once value types are implemented in the JVM. OCaml and F# look interesting, I haven't evaluated these carefully.