There is no current plan to support MQTT for OSBee — OSBee is meant to be a low-cost latching solenoid controller for 3 zones. Now that we have stared selling OS 3.0 Latch, it’s unlikely there will be any future firmware update for OSBee. In comparison, OS 3.0 Latch controls 8 zones, and runs standard OpenSprinkler firmware. We are working to add MQTT support for the standard OpenSprinkler firmware.
That said, given that OSBee is open-source, you can feel free to modify the firmware to add MQTT. It shouldn’t be that difficult as the code base is similar to OpenGarage, and we already have MQTT support for OpenGarage.