A complete rewrite of a large project is risky anyway. Doing so in a language in which literally no other project of that size exists yet strikes me as insane.

I love Swift. But I've been adopting it in bits and pieces over the years. It's not just that the language has changed significantly, you also have to get used to the idioms. E.g. my early Swift code often featured Pyramid of Doom patterns, and both language innovations and better familiarity with the idioms have helped a lot with this.