From SS Web site:
If you retire at full retirement age in 2016, your maximum benefit would be $2,639. However, if you retire at age 62 in 2016, your maximum benefit would be $2,102. If you retire at age 70 in 2016, your maximum benefit would be $3,576.
The above FRA benefit works out to be $31,668/yr for a 66-year old now, and for a 70-year-old it is $42,912/yr. That is for a worker who maxed out SS contributions for 35+ years.
Based on that, I believe your quoted future benefit is in terms of today's dollar, but only if you keep on working many more years.
By the way, SS benefits are based on your highest 35 annual
indexed incomes. Hence, working one more year only helps if it allows an earlier lower-pay year to drop out of the computations.