Pandemics have absolutely been on the radar. We already had plenty of hints: SARS, swine flu, heck the great influenza pandemics of the past. Increasing total population, increasing population density, and increased travel have been obvious risk factors for as long as anybody has talked about this stuff.
one of the striking features is that every 10 years or so
There are multiple things every decade. In the past 10 years we've had the pandemic, something resembling a coup in America, war in Europe, a nuclear disaster, accelerated global warming, and so on.
Trying to fit it into a shallow truism like "every 10 years, it's something!" is some kind of magical lazy thinking, right up with "it takes 10,000 hours to master a thing!" and "celebrities always die in threes!"
It wasn't stated as a truism. It was stated as a practical limit to our ability to naively project the future forward. And therefore the centuries long sweep of Foundation fails.
Trying to fit it into a shallow truism like "every 10 years, it's something!" is some kind of magical lazy thinking, right up with "it takes 10,000 hours to master a thing!" and "celebrities always die in threes!"