Your Stack Setup
If you do not have budget and time to overhaul your architecture, you may consider focusing on your endpoints and gateway. It is common to setup integration gateway to manage the translation of XML to JSON. This provides backward compatibility to your legacy architecture. In another words, you gain more time to progressively upgrade your stack. The good part is that these integration gateway can serve as a command post to manage your endpoints.
The switch from XML to JSON is a time consuming effort. If you do not have legacy system with XML, you may want to consider having a technology stack that favors JSON. However, those with legacy and XML integration may want to lower risk with the setup of integration gateway to manage your endpoints and translation of XML to JSON.