Medicare Projected Expentitures

2012 572
2013 607
2014 643
2015 676
2016 716
2017 760
2018 810
2019 865
2020 932

Source: http://www.cms.gov/ReportsTrustFunds/downloads/tr2011.pdf , pg. 51, Intermediate estimates.

After 2020, the projected expenditures are given as a percent of GDP as follows.  Percents for dates between these would be interpolated.
2020 3.99%
2025 4.59%
2030 5.16%
2035 5.56%
2040 5.77%
2045 5.87%
2050 5.94%