We use templates, exceptions, STL, and Boost and deploy to tens of thousands of devices in the field. We have the advantage of a uniform hardware and OS platform, so we don't have to worry about compiler issues.

We could reasonably replace C++ with a combination of C and a higher-level language. However, C++ is a much better language for our low-level code than C, and we have a lot of low-level code, so we have to take it seriously. If we took the route of using a high-level language to coordinate functionality implemented in C, we would end up using C++ to implement the "C" libraries, just for the benefits of RAII, exceptions, smart pointers, etc.

We could also succeed with a stable and efficient Common Lisp implementation. Other languages such as OCaml might work for us, but I'm not qualified to say.

We wouldn't bother changing at this point, though, unless we decided to create an entirely new product to compete with our current one. C++ is not a problem or a limitation for us. The shortcomings of C++ add a little bit of extra work, but they aren't a multiplier. Most other languages would aggravate our existing problems instead of just adding a constant factor of inconvenience.

And that's with templates, exceptions, STL, and Boost!