The MCU has slowly been expanding its cosmic mythology through the Thor and Guardians of the Galaxy movies, and next year’s Avengers: Infinity War will explore those corners further when Thanos attempts to obtain ultimate power through the Infinity Stones.
If that can’t happen, then at the very least they could relay important pieces of history, like how The Collector explained the Infinity Stones’ origins in Guardians of the Galaxy.
There may be a way for them to provide information in a moment of need without technically breaking that oath.
Marvel Studios president Kevin Feige has admitted that the plan is to place more focus on MCU “cosmic universe,” and hopefully that means that the Watchers will receive significant attention later down the line.