From the paper: 'Even for very long 100-year projection horizon, with the most radical life extension scenario (assuming no aging at all after age 60), the total population increases by 22% only (from 9.1 to 11.0 million).'

That stat is for Sweden—in case anyone wonders where the numbers are from.

Anyway, that's for the next 100 years. In 5000 years one would hope the human race will be multi-planetary. Looking at the time-scale, concern is still misplaced.