A study published this week calculates life expectancy of a newly diagnosed HIV person at 24 years... I thought life expectancy had gone from limited to unlimited with new treatments? What gives?

This is a statistical artifact. The estimate you quote is based on the real numbers that exist, on which we can calculate mortality. These numbers show the life expectancy you quote. However, it is important to note that this calculation, redone every year based on new information, keeps getting longer and longer. It is a fact that newly infected patients who go on treatment as soon as their CD4 counts begin to decrease are not experiencing any measurable disease progression in the vast majority of cases. Based on these observations, it is likely that people who become infected with HIV in 2007 will likely live out their lives without evidence of disease progression.