When Tate Modern decided to rearrange its collection around a series of vaguely defined “hubs,” many in the art world were skeptical. But the rehanging has been a major hit with visitors, and other contemporary art museums around the world are beginning to experiment with ways to make their permanent collections seem less, well, permanent. “With contemporary art, where history is still fluid and museums have yet to become pantheons of unchallenged masters, flexibility seems advisable.”