It's not clear how much experience the author really acquired with each language, and whether that experience was sufficient experience to justify his statement: Go felt that way to me — it was good at everything, but nothing grabbed me and made me feel excited in a way I wasn’t already about something else in my ecosystem. He's apparently using each language to write relatively small command-line utilities. If Go is…
I (and many others) "still" use C++ (which is a very different language from C) in 2014 because it's an extremely powerful language that's still evolving and has produced many innovations that haven't been replicated by many other languages, such as destructors/RAII, strong compile-time type checking, generic programming, and ownership/move semantics. To me, Go looks like an update of C that has ignored all the good innovations of C++. It has no destructors, uses GC instead of ownership/move semantics, and requires runtime type checking instead of providing generics. I see it as a big step backward from C++, so unlike Rob Pike I'm not surprised it hasn't attracted C++ programmers.
Rust, on the other hand, has taken many of the good parts from C++ and developed them even further, without the baggage of C++. Thus, while I haven't coded any Rust yet, it looks like a step forward from C++ and has me quite excited.