It's already quite popular. I'm less convinced there's a large pile of people wishing for a fairly high performance garbage collected language that are not using Go because of this. There just aren't many viable alternatives.
Java and C# being the obvious (and more performant) alternatives. And compared to them, Go already wins because of not being, well, "enterprisey". And with that I mean less the languages itself, but also the whole ecosystem around them.
There are definitely lots, I'm one of them. I use Scala, which is very powerful and imho much nicer language than golang. But the tooling and other support is slow and subpar. But I just can't go back to a brain-dead language(!) like golang because it hurts to program in such languages to me. So I hope that either golang catches up with Scala's features, or that Scala catches up with golangs tooling.
And I think there are many similar people like me.
Scala is overcomplicated esoteric programming language. It is great for obfuscation contests. It is awful for production code, since Scala code lacks maintainability, readability and simplicity properties.
Perhaps, but other languages that look a lot like Go with these additions (e.g. OCaml) have not gained much popularity, despite getting much more love on forums like HN. It's important to remember that the people expressing strong opinions about sum types on the internet are a tiny and non-representative fraction of working programmers.
I blame C# for the confusion. Think of it this way: the ability to explicitly express a type Foo|null implies the existence of a non-nullable Foo as well. IOW it’s shorthand for “nullable and non-nullable types”.