It is pretty gloomy.
The American economy is running on empty. That's the hypothesis put forward by Robert J. Gordon, an economist at Northwestern University. Let's assume for a moment that he's right. The political consequences would be enormous.
In his widely discussed National Bureau of Economic Research paper, "Is U.S. Economic Growth Over?" Gordon predicts a dark future of "epochal decline in growth from the U.S. record of the last 150 years." The greatest innovations, Gordon argues, are behind us, with little prospect for transformative change along the lines of the three previous industrial revolutions:
Over most of human history, in Gordon's view, the world had minimal economic growth, if it had any at all - and "there is no guarantee that growth will continue indefinitely." Gordon's paper suggests instead that "the rapid progress made over the past 250 years could well turn out to be a unique episode in human history."
An open access version of The Gordon article is here, although I haven't read it yet. It sound similar to Tyler Cowen's arguments.