Probably that also, but that's not the whole story. As with AIDS there are often many maladies and problems along the way. It would not be honest for a person with AIDS to say they had pneumonia if they had both AIDS and pneumonia.
Just bringing up AIDS as a possibility means you know nothing about AIDS. Today HIV is a manageable disease in developed countries. Tens of thousands of people have been HIV positive for more than 30 years and are doing just fine on modern HIV meds. These meds are so good that high risk people who are negative take them prophylactically to prevent them from getting it from an accidental exposure.
Pneumocystis pneumonia, an opportunistic infection that was the major cause of death in the early days of AIDS, and still is a problem for cancer and transplant patients, is easily treatable these day, not to mention that there is a very effective vaccine that is given to anyone that may be at risk, including the elderly.
In the western world, the number of people who go from HIV+ to full blown AIDS is a fraction of a percent. These people usually have other issues, such as Hep-C, or a drug addiction where they repeatedly go days forgetting to take their HIV meds.