I also don't expect that a lot of the existing Java code will be rewritten in Go. But there exists a whole array of startups/unicorns today who use Go extensively. Many of them will grow into enterprises. I predict that Go will generally hold up well for them as they scale. They will feel a lot less of an urge to switch to something more mature and scalable like Java, as many companies who started out with Ruby, Scala, or PHP did.

I often see enterprises using a mix of languages and technologies (depending on how independent the different org units within it are) and some amount of Java fatigue in developers who are not retiring in less than a decade. Go is often amongst the top choices they are exploring.