As far as I can tell, the Réunion flaperon is the only piece of debris discovered so far that has a reasonable probability of coming from the plane.
And that is most likely the only piece that will be found, why this piece and no others, well that could be due to its location on the aircraft and the rather large object directly in front of it, one can easily imagine a sequence of events that would see it detaching as the aircraft landed on the water, whilst other parts would stay attached as with the scully landing, if anything else was to wash up somewhere it would likely be the other flaperon, but that would be pure chance.