If you have a running application with FDT 1.2.x there is no reason to update it. You should think about an implementation of FDT2.0 when planning a new application/plant and your DCS system provider supports FDT2.0. However, if you would like to benefit from the improvements of FDT2.0 you can update your application.. All DTMs based on FDT 1.2.x are useable in the new FDT 2.0 frame application.