I cannot comment on whether there is a 2.x version of the binding in works or planned to be developed. But what you can do when OH 3 comes out if there are no plans to develop a compatible binding includes:
- stick with OH 2.5
- run an instance of OH 2.5 (or 1.x) to support your 1.x bindings and use Marketplace MQTT Event Bus. (NOTE: I’m working on some improvements to the Event Bus which should make setting it up and using it easier, will be released in the coming weeks and I’ll post at that link with the new code when it becomes available).
- interact with PiFace using shell scripts or Python and control it from openHAB using the Exec binding/executeCommandLine
- set up a separate service that interacts with PiFace and integrate that service with openHAB (MQTT is a popular approach).