Hi Kathleen,
It depends on what the change is: if rhew change contains new data that is relevant for you to import: then yes. You will need to make a change in the import mapping and in the logic of your application to deal with the new data.
If the json is only extended in parts that are not relevant to you, there is no need to change anything. Mendix will usually ignore data that does not affect the mapping.
Is this what you are looking for?
Michiel