Do they mean that the average life expectancy at birth will not exceed 115? Because the article opens by noting that the current record is 122, so obviously some individuals will exceed 115, seeing as several already have.
The only claim it managed to get across to me was that we can expect the end of the lifespan bell curve to get steeper and steeper as average lifespans continue to increase from better longevity, while maximum lifespans (and the number of people who reach them) increase at a much slower rate.
The abstract for the paper itself ( http://www.nature.com/nature/journal/vaop/ncurrent/full/natu... ), seems to only discuss the statistical existence of an aging limit, not the biological mechanism(s) causing it.