Tableau Server can connect live to the JSON file as a data source connection. JSON File - Tableau But connecting to JSON stored data on another database is slightly different.
There should be more information on this request in the following Tableau Community discussion Can Tableau process JSON data?
I would submit an idea to the Tableau Community Ideas space for this feature. The Tableau Product Managers review the ideas space for new features to be added to future releases.
Hope this helps!