Rust is going to be used often, but we are open to other choices when they make sense.

Since most unsafe code is C or C++, Rust usually makes the most sense for rewriting one component at a time. It integrates with C and C++ very cleanly because it has good FFI and no runtime.

If we were rewriting more projects from scratch and integration with existing C and C++ code was not important, we might use other languages more often. I don't expect we'll attempt to rewrite many pieces of software from scratch.

Source: I run the memory safety initiative at ISRG.

The quote you provide above doesn't specify that these rewrites are to be in Rust and I don't think you've contradicted the parent in any way. The examples have been in Rust but the foundation doesn't seem to insist on rewrites being done in a specific language. As an aside, the foundation doesn't seem to be much more than a collection of papers at this point.

The "memory-safe languages" may mean Go, Java and a bunch of other less popular languages.

In the end of the day only Rust will be chosen because we are talking mostly about system infrastructure.