As much as I like rust, I feel the statement is a bit premature.

Rust has only one real compiler and no independent language standard.

Rust is also the only alternative that is really being discussed most places. For an idea as major as "deprecate C/C++" you really want a couple solid alternatives. Rust is not perfect for everything, and so its easy to pick on the weaknesses and say "that's why we're sticking with C/C++".

I guess Ada or D are viable alternatives, too, and maybe need more attention. But the tweet only mentions rust.