Here is a good discussion of the math involved.
https://www.youtube.com/watch?v=Kas0tIxDvrg
It doesn't appear that "we are all going to get it" in this 1st season at least, but 20% might and that is a very big number. We have more control over the spread than we think and it's closest biological relative SARS CoV-1 2003 was contained at 8000 cases. We are far beyond that now but the process of containment is the same and the sooner we get below an infection rate of 1, the sooner this thing becomes self limiting.