The question of language longevity for new languages
Every so often I feel a temptation to rewrite DWiki (the engine behind this blog) in Go. While there are all sorts of reasons not to (so many that it's at best a passing whimsy), one concern that immediately surfaces is the question of Go's likely longevity. I'd like the blog to still be here in, say, ten years, and if the engine is written in Go that needs Go to be a viable language in ten years (and on whatever platform I want to host the blog on).
Of course this isn't just a concern for Go; it's a concern for any new language and there's a number of aspects to it. To start with there's the issue of the base language. There are lots of languages that have come and gone, or come and not really caught on very much so that they're still around but not really more than a relatively niche language (even though people often love them very much and are very passionate about them). Even when a language is still reasonably popular there's the question of whether it's popular enough to be well supported on anything besides the leading few OS platforms.
(Of course the leading few OS platforms are exactly the ones that I'm most likely to be using. But that's not always the case; this blog is currently hosted on FreeBSD, for example, not Linux, and until recently it was on a relatively old FreeBSD.)
But you'd really like more than just the base language to still be around, because these days the base language is an increasingly small part of the big picture of packages and libraries and modules that you can use. We also want a healthy ecology of addons for the language, so that if you need support for, say, a new protocol or a new database binding or whatever you probably don't have to write it yourself. The less you have to do to evolve your program the more likely it is to evolve.
Finally there's a personal question: will the language catch on with you so that you'll still be working with it in ten years? Speaking from my own experience I can say that it's no fun to be stuck with a program in a language that you've basically walked away from, even if the language and its ecology is perfectly healthy.
Of course, all of this is much easier if you're writing things that you know will be superseded and replaced before they get anywhere near ten years old. Alternately you could be writing an implementation of a standard so that you could easily swap it out for something written in another language. In this sense a dynamically rendered blog with a custom wikitext dialect is kind of a worst case.
(For Go specifically I think it's pretty likely to be around and fully viable in ten years, although I have less of a sense of my own interest in programming in it. Of course ten years can be long time in computing and some other language could take over from it. I suspect that Rust would like to, for example.)