In a company that I've been working with, this approach has been used for over 8 months already: most work is done on C++ side and then exported via simple DLL interface (flattened C-style methods) to Delphi. Generally C++ compilers produce much more efficient code (see (1) and (2)), so the performance is better than never and you have overall piece of mind that code is sufficiently future-proof. It seems that C++ community has grown massively since introduction of C++11 (and C++14, now C++17) and with large investments from big players like Google, Apple and Microsoft, it is not going anywhere any time soon.