I was actually wrong, order book opened in May and
deliveries started in June. Those cars would have been on 19 plates.
Tesla have sold more cars year on year in the UK. From Car Dealer Magazine:
They
sold 25,171 Model 3s alone in 2021.
All of that is to say that there have been more and more Teslas (particularly Model 3s) being delivered, year on year, since they came out. The shock from Q3-Q4 2019 cars coming off lease and hitting the market is a phenomenon that is going to be repeated for every quarter from here on out.
I'm not sure the BMW comparison is valid because the BMW M140i was around for 4 years and ceased production in 2019. Cars that drop out of production can sometimes appreciate (depending on volume), particularly if they are better in some ways than later cars (M3 CS and CSL pricing makes me sad - I missed out on picking one of those up).
There is no "slowing to a constant steady stream" with Tesla. They are all about volume.