I'm afraid that if there isn't a nasty economic slide, the left is toast. Anwar Sheikh's hypothesis about a nascent rising long-wave looks increasingly plausible to me. U.S. manufacturing seems to be recovering (how the fuck did that happen, incidentally?!?)
Doug is right that a rising wave helps strengthen the class power of workers, but that power can only be leveraged into progressive politics if there is some ideological basis for opposing capitalism. The Golden Age at least confirmed the possibility of successfully regulating capitalism -- another Golden Age now would only confirm the success of deregulating it.