I haven't looked at Swift, at all. I don't buy Apple products, so have no familiarity with their ecosystem. But, now that it's been opened up, I'll have a look at it, though it seems likely to remain predominantly a language for Apple products for the foreseeable future (I think?), so not something I'd find myself using in production any time soon. But, I guess we'll see how that shakes out over time now that it is open.

Given the rate at which JavaScript is converging on a really nice set of modern features and is having warts removed and performance is accelerating, I wonder if any other language is as relevant long-term.