> But it's an Elon Musk promise, so how much weight do you put on it?

Zero.

And I really mean zero, not a negative value. That is, when Elon Musk promises something, it doesn't mean he won't do it, it means that it is just as likely to do it as if he didn't promise anything.

I don't understand why people listen to him when it comes to predictions, he is as close to a random generator as one can get. Even analyzing his actions come with a lot of uncertainty, though not as much as what he says, some things are too big to hide. Being able to maintain such level of uncertainty is probably part of his success, he is like a poker player no one can read.