Must Culture Have Momentum?

Peter Aspden of the Financial Times recently wrote an article titled "Of Classicists and Carbuncles", about the Prince of Wales' ongoing crusade against modern architecture. I see little need to write about the topic; others have done so. But what interested me was a particular passage in Aspden's article. He writes:

Can we really not move forward? This is the element of modernism that the prince most misunderstands. Culture must have momentum. It has to look ahead. That is its point. By definition, culture acts as a commentary on its own time, but occasionally it has to look beyond it, to anticipate what is to come.

Thus, Aspden is making the argument that culture should be progressive. Not because there is some teleological goal of goodness toward which it must strive, but simply because it needs to be going somewhere.

So I ask of our readers: First, must culture really always be going somewhere? And second, if that is the case, is going "backward" an acceptable option, or is antiquarianism antithetical to the future-oriented movement of culture?