I think it’s very likely some of each. Assuming we are talking of a scenario where there is sufficient testing where we can be assured we aren’t introducing ne

I think it’s very likely some of each. Assuming we are talking of a scenario where there is sufficient testing where we can be assured we aren’t introducing new bugs, it’s probably a good idea to do rewrites after a couple of decades have passed, and to use whatever the state of the art respected language is, is if it has demonstrable advantages.