It has already happened in parts of the country and more water utilities may switch over to a new chemical treatment for drinking water. Chloramine has been used as a disinfectant since the 1930s, but many water utilities still primarily use chlorine treatments. The San Francisco Public Utility Commission recently made the switch in part because chloramine is considered to be more stable than chlorine for water treatment.
One of the drawbacks of the switch is that chlorine can be boiled out of water and will dissipate on standing, but chloramine will not dissipate in water. Water treated with chloramine should not be used for kidney dialysis machines or for fish tanks unless it is treated with a water filter first. If you need a filter system certified to reduce chloramine I recommend the Culligan US-EZ filter system as a simple point of use filter.
Many public water utilities will switch to a chloramine treatment once per year to help balance water treatment. You should be notified by your water utility prior to any change in treatment.
You can click on this link for more information on chloramine in drinking water.