Assuming federal revenue generating laws and spending laws remain the same, the federal debt as a percentage of the GDP will actually bottom out within a few years, before starting to increase again around 2020. This is according to a graph in the Congressional Budget Office offers a graph in their Budget and Economics Outlook: Fiscal Years 2013-2023 study.
The public held debt will reach 76 percent of GDP by the end of this year, but will decrease to 73 percent by 2015. This will bring the debt to around the levels of 1950. A rise back up to 76% is expected around 2020, followed by a reasonably even increase each year. Don’t expect the debt to get to the World War Two rate of over 100% of the GDP anytime soon though.
Indeed, according to the chart the 1940’s saw the highest rates of debt in the nations history, with it not until the 50’s that the debt as a percentage of the GDP started to shrink to the level of the debt today, brought about in part because of a growing economy that drastically increased the size of the GDP, and a string of budget surpluses and or smaller deficits.
More revenue and/or spending cuts could lead to a lowering of the debt as a percentage of the GDP in the near future.