JVM developer here, I think it has legs, but it's a couple years away from truly being a threat to Oracle and Java. The VM, tools and libraries are a lot less advanced and or non-existent in comparison to JVM-langs.
If developers hop on board and start building the ecosystem then I think Oracle should be concerned. That could take anywhere from 2 to 10 years IMO.
"Perhaps the final straw was what Gosling said was Oracle's move to rein him in. indeed they owned Sun and thus Java, so they also owned its creator and his intellectual property, so it was up to Oracle to decide what Gosling or anybody else had to say about Java."
But this doesn't really make any sense... Sun was a historically bad steward of Java after 1.5. Oracle has done a lot to advance the language and ecosystem since acquisition.
If developers hop on board and start building the ecosystem then I think Oracle should be concerned. That could take anywhere from 2 to 10 years IMO.