I can picture all of those things happening to some extent and still would only estimate a 3-5x reduction in fleet size. In order to get 10x, you are implicitly estimating that rush hour vehicle utilization is currently only 10%. I would estimate that rush hour utilization is in the range of 50-70%.
For 10x, you would absolutely have to do something to address peak time behavior. For example, if Mom, Dad, and Junior all have to be somewhere at the same time, you are still gonna need 3 vehicles. In aggregate, total fleet demand will be dictated by the marginal demand at the peak of rush hours.
EDIT: to add, I would still predict a massive move of car ownership toward corporations, and their primary domicile to large parking lots in outer suburbs, only to awake during rush hours. These cars will have a much lower return on investment, but probably enough to justify their costs.
For 10x, you would absolutely have to do something to address peak time behavior. For example, if Mom, Dad, and Junior all have to be somewhere at the same time, you are still gonna need 3 vehicles. In aggregate, total fleet demand will be dictated by the marginal demand at the peak of rush hours.
EDIT: to add, I would still predict a massive move of car ownership toward corporations, and their primary domicile to large parking lots in outer suburbs, only to awake during rush hours. These cars will have a much lower return on investment, but probably enough to justify their costs.