I'm surprised at the list. Rust is fundamentally immature, C++ is fundamentally intractable, Python is fundamentally unusable at scale, and Hack is, well, no discussion needed. Strong negative signal for potential candidates.
I can't speak to the other three, but the comment about python is not accurate. Or at least not given the way that python is used for the mentioned applications "For data science, ML applications, and Instagram, Python continues to be the language of choice".
Pure python maybe, but the popular packages for these applications are all essentially python wrappers for highly optimized compiled code.
I'm curious though, what language(s) do you believe belong on that list?
Instagram is a huge Django app and unlike all the ML libraries, Django isn't highly optimized low-level code wrapped in Python, at least not by default. That's why Facebook are putting so much work into running a more performant fork of CPython - https://github.com/facebookincubator/cinder