That is true, the only real question is the peak rate of sales, and how long sales remain elevated.
There is a "one time" build out of the Robotaxi fleet, it it might be larger than expected, because many people without a convenient transport option might gain one.
My best guess would be around 10 years of elevated sales, perhaps 2028-2038 or something like that.
Once that peak has passed, the overwhelming majority of the fleet are EVs and the Robotaxi fleet is built, sales may drop fairly rapidly, even with a larger percentage of the world's population having a car based transport service.
Tesla seems like one company well positioned to tap the peak... having the ability to make 20 Million EVs in 2030, might be more important than having the ability to make 40 Million EVs in 2040.
Post 2040 Tesla is mostly trying to sell customers an improved version of their EV, EVs will get better and cheaper, and the closest parallel is a smart phone. Like a smart phone, sales probably will not be based on the "basic" functions. Great FSD, good entertainment, good software apps, good internet connectivity, brand, aesthetics and comfort, will all become more important. Customers will need to be convinced they need the latest and best EV. Unlike phones, EVs cost a lot more, and selling a new one to an existing customer will not always be easy.