If it was too slow in Python and now moving to Go. Could there a time when there is a need to move to Rust/C/C++ for even faster performance? Go seems an odd choice based on performance consideration alone.
I'm not an expert in Rust, but from what I know it seems like moving to Rust would require much more rewriting than Go.
The other thing, as he says in the post, is that you get diminishing returns: The Go code was 20x faster than the Python code, but the whole 7-hour operation was only 10x times faster, because at some point the external SVM calls start to dominate. So even if a rewrite into Rust could gain him another dozen percentage points in speed, it's unlikely that a rewrite into Rust would have much of an impact on his end-to-end performance; and it would almost certainly make the code less accessible.
If you consider the could, there's always a way to make things arbitrarily more complex. Reality is that your target is simply "sufficient".
Also another provided reason was language consolidation, so ease of developer-project-flexibility was probably not the lowest of concerns