That's likely what's happening. Owner buys it new, uses it for 7-9 years. Goes to the used market, where it gets 4 years. Maybe a second turn on the used market, and then it gets sold overseas. I hear the Middle East is a big consumer of used cars from the US.
Also, "aging" is going to be heavily influenced by socioeconomic group. For some people, aesthetic damage to the paint or interior is enough to qualify as aging. Other people are more interested in the functionality, and other people are interested in whatever drives. I have friends that consider a 3 year old car to be aging, and I have friends who drive 10 year old cars and think they're just fine.
I do think Teslas (and electric cars in general) are going to have an impact on the used car market, especially on the cheaper end. These batteries don't have tremendously long lifespans, and a replacement often costs as much as a cheap ICE car.
I'm curious if there's going to be any profit in repairing electric cars with new batteries to sell them in Mexico or other parts of the globe, or if we're basically just going to be cutting off part of the used car market. The social impacts of developing countries losing access to a relatively cheap supply of vehicles could be bad.