you're right if one assumes a linear growth, but the reality is that it has an exponential growth. See https://www.youtube.com/watch?v=Kas0tIxDvrg for a short intro.
most likely those more susceptible get it first
it is not clear what percentage of the population would either not get it or if they do get not get noticeably affected
Here's a tip: it still comes out to be 5-10x higher than the seasonal flu.
With an R_0 of 2.4, approximately 60% of the population can be expected to contract the virus within a few months, unless mitigation measures are taken.