>Maybe the replacement with JSON is quietly happening already but XML is still recommended and thoroughly supported by governments. Is it maybe time to focus on standardising mappings and transformations from XML to JSON in case there is an inevitable >switch to JSON away from XML for government data/document submissions?
I think I can directly address this comment as well as your original question at least wrt US govt IT without saying anything I shoudn't.
In the US there is a legislative requirement for federal agencies to develop and maintain enterprise architectures
really then, your question boils down to whether government EA can be built and maintained on JSON.
Simply put either government agencies will have to be convinced that the impedance mismatch that JSON has for enterprise data modelling has been addressed or that law will have to be changed.