I think good support for SIMD will go a long way. C++ is also pretty slow on its own, but with SIMD intrinsics (or lucky autovectorization [1]) it can be speedy

I think good support for SIMD will go a long way. C++ is also pretty slow on its own, but with SIMD intrinsics (or lucky autovectorization [1]) it can be speedy. We're talking typically about 1.5 - 10x speedup in performance sensitive code with SIMD vs plain C++. Highest speedup I've seen was about 40x in sorting code. SIMD is a sorting demon. That said, I want safety more than speed. Speed I can get by writing an unsafe extension in C/C++. Safety is very hard to achieve in C/C++. Getting it right is the first priority. That's why I see Rust being used instead of where traditionally C++ is the default. Or some other new language that can fill C++'s shoes. Rust does seem like the strongest candidate at this point. I'm confident Rust and Golang performance will improve as the projects get more mature. The generated code is full of optimization opportunities. [1]: Autovectorization optimizations by C++ compilers tend to be fragile, small changes will undo them. So far easier to use intrinsics than figure out the black magic for autovectorization optimizations.