World Population Prospects: The 2006 Revision
In the next 43 years, world population is expected to increase by our total population statistic in 1950, 2.5 billion.

The United Nations Department of Economic and Social Affairs, the Population Division provides this direct link to tables.

“The world population continues its path towards population ageing and is on track to surpass 9 billion persons by 2050, as revealed by the newly released 2006 Revision of the official United Nations population estimates and projections.” (From the press release).