Over what timeframe do you expect this to happen? It'll take at least 10 years for a new default on all systems (which is a challenge in of itself) to propagate

Over what timeframe do you expect this to happen? It'll take at least 10 years for a new default on all systems (which is a challenge in of itself) to propagate to the point where you could rely on it. There's also the question of what new language is worth the cost of the transition period (no new shell I've seen justifies the change).