250,000 a year is a huge number, but Ford F-Series pickups almost reached 900,000 in 2019, so it's theoretically possible.
Elon Musk has suggested during Tesla Battery Day that the company may produce a quarter-million Cybertrucks a year: "There's probably room for at least unit volume of 250,000 to 300,000 a year, maybe more."
We already know that the number of pre-orders is high - well over half a million, maybe even 600,000 according to Musk - but is there such a high demand for the Cybertruck, especially since the sales would be limited to North America?
For comparison, Tesla Model 3 never crossed 200,000 annually in the U.S. Tesla Model Y still has to prove itself (we don't know its sales results), but anyway, at 250,000 or more, the Cybertruck would be one of the most popular Teslas and EVs in general.
Because the production of the Cybertruck is scheduled to start in 2021, and we have to include the ramp-up phase, the full production probably will not be achieved earlier than at some point in 2022, maybe even 2023.
According to the Automotive News' article, the Ford F-Series pickups noted in 2019 more than 896,000 sales, while the Ram pickups were at 633,000.
We can guess then that selling 250,000+ of Tesla Cybertrucks is theoretically possible, but Tesla would have to conquer 10-20% of the market share.
By the way, the Cybertruck is expected to be classified as a medium-duty pickup (like the Ford F-250 Super Duty).
The rest of the world will not get such a big electric pickup and has to wait for an eventual smaller, but equally cool version.