I'd say 2018, based that the previous business cycles (with the exception of the last one) lasted about 9-10 years.
Well the previous boom lasted only 5 years, the one before that however from 1992-2001 was the longest on record, 9 years.
If we can take care of the external factors dragging our economy down(energy, health care, and debt) as well as deal with the Macro-economic stablization and recovery we should be able to enjoy a long period of sustained rapid growth. However the chances of all these being dealt with is minimal so I say we have another in 2013 or 2014, unless of course we have another Leg down in this one in 2010, then all bets are off.