Look at it a different way. How many years is the average car on the road? Even if we banned the sale of new ICE vehicles today, it would still take well over a decade for them to filter out of operation.

But there are very real, very possible existential crises that could massively impact the ICE fleet and filter out existing vehicles faster the usual replacement rate. To obvious examples: the cost of gas rises fast enough, and/or entire gas chains go out of business making stations hard to find.