json will be mocked in a few years by the same people that today mock xml. In the end, unix always survives.
XML is native to nothing. It's annoying to use everywhere.
UNIX tools just don't compare. Sure, they stick around, because sometimes they're the easiest tool for some job, until they aren't and you regret starting out with them.
In a few years, Javascript and Javascript-compatible languages are likely to be bigger than ever before. A whole generation of developers has been trained mainly on them. Billions of dollars have been invested into the ecosystem. Whether we like it or not, that's the reality. For that reason alone, JSON will stick around.