The first year for a system isn't high compared to year 2, 3, and/or 4. So I'll say 10-12.5 mil. I think sales will slow down in the Spring and Summer time.
So by shipped numbers if Sony releases them:
Jan - March: 2 - 2.5 mil
April - June: 1.5 -2 mil
July - Sept: 2 - 2.5 mil
Oct - Dec: 4.5 -5.5 mil
2022 I predict will be 15 -17 mil.