I wonder, do we expect the rate of pandemics to increase or decrease over time?
On the one hand, you might assume the rate of pandemics is proportional to the size of the human population; more people, more hosts for mutating viruses, greater odds of one mutating to a pandemic-causing disease. There have been roughly 400 billion person-years lived since the last pandemic, but given the larger populations, we'd expect to accumulate another 400 billion person-years by around 2070.
On the other hand, you might assume the rate of pandemics is proportional to the size of the animal populations humans interact with. More animals to breed the viruses, more interactions to pass along the next candidate pandemic. In this case, we might expect more than a century for the next pandemic, since the next century isn't expected to be nearly as kind to animal populations.
(Obviously the situation is more complicated than an either-or, and has many contributing factors, and is stochastic in any case.)