There's a huge gap between "20 years from now, we won't die as quickly as people born in 1900" and "20 years from now, people will live four times as long as th

There's a huge gap between "20 years from now, we won't die as quickly as people born in 1900" and "20 years from now, people will live four times as long as they do in 2013." The former is quite likely. The latter is pretty far out there.