When I ordered my Model 3 in November of last year, 2020 models were already being delivered. Mine was a 2020, built the first week of December, 2019. The VIN tells the tale. Count back eight places from the end of the VIN. That character represents the Model Year. For 2020 the character is an "L". 2021 models will likely have an "M". My Model Y may build this month. Would be nice to have it a 2021. It doesn't necessarily indicate a change in the product itself - especially with Tesla - but is just a convention of the numbering system. Domestic manufacturers often begin the swap around this time each year.