It's very simple and it has nothing to do with identifiable goals. It is to keep thinking about what architecture can be, in whatever form. That is an answer, isn't it? I think that S, M, L, XL has one beautiful ambiguity: it used the past to build a future and is very adamant about giving notice that this is not the end. That's how it felt to me, anyway. That is in itself evidence of a kind of discomfort with achievement measured in terms of identifiable entities, and an announcement that continuity of thinking in whatever form, around whatever subject, is the real ambition.