1. Very limited libraries.

2. Very limited support from enterprise vendors.

3. Poor at scaling to hundreds of developers. Java's verbosity and over use of design patterns has actually been beneficial.

4. Network effects. Almost every enterprise developer, outsourced dev shop and operations team knows at least a little Java.

Well of course everything you said is kinda true. Go is not going replace Java in one-to-one replacement type projects. It is going to be in a way like Cloud vendors have creamed traditional IT/outsourcing vendors or IPhones crushed blackberry.

At some point existing Java systems will stop delivering value compared to their maintenance cost in lot of situations. This is where Go as replacement will come in handy.