Danish researchers have reported that projecting past life expectancy forward suggests that half of the babies being born now can expect to live to 100. Perhaps. Making projections over that sort of timescale are very difficult, and it is dangerous to give information like that without also giving an indication of the uncertainty around the central estimate.
Perhaps this is the way life expectancy will head, but I have my doubts. Most of the past improvements have been related to fairly broad-based improvements – improved sanitation, the discovery of antibiotics, people giving up smoking – and reducing mortality going forward will be much more difficult. For example, cancer is now the major cause of death, rates of mortality from heart disease having fallen so substantially over the last thirty years. But cancer is a term used to describe literally hundreds of different diseases affecting many different parts of the body, and crucially with many different causes. Treating each of these will not be straightforward, and in most cases the treatments will extend life but not cure the disease. There is also the risk that lifestyle changes (in particular obesity) will cause an increase in the incidence of some cancers, and even that rates of heart disease will start to increase in spite of medical advances. Certainly, an average life expectancy of 100 for newborns is optimistic.