I am not sure your hypothesis is correct. You tie the current, worldwide economic malaise to a shortage of cheap energy (ie. easily obtainable oil supplies). However, it is quite possible that developed countries will transition from using oil as a fuel to utilizing some other source. We (the world) have ample supplies of coal and we are quickly reaching the point where we can tap into clean sources of energy from the sun and from wind. Who is to say that once the price/industrial requirements of oil reaches a certain point, society won't invest the resources necessary to make the shift?
In short, the economic issues we face right now (in the U.S. and throughout much of the developed and developing world) might more closely resemble the Gilded Age in America than the late Roman Empire (which also suffered from resource shortages). Whereas the economic problems in the U.S. during that period (and again in the 1930s) signaled a shift from the 1st Industrial Age to the 2nd Industrial Age, the current economic woes are only a hiccup between economic modal types. In this case, from the Information Age, which itself started up during the 1970s stagflation period, to the Internet/web-based Age?