Realistically, without access to the US market, the goal of overtaking Toyota is difficult. Also important to note, this is single brand sales, not group sales, so there is still a lot of room for development.
WSJ: BYDs found at the bottom of Yangtze River
Overtaking Toyota would occur once Toyota is pushed out of the Chinese market.
Last year, Toyota sold 2.1M in the US but 1.94M in China. That 160K will be more than made up by the growth of the Chinese market which as China's per capita income increases is expected to be up 38M by 2030.*
I think that is a conservative figure. Rapid increase in per capita income plus more affordable cars plus massive expansion and advancement in charging infrastructure means we should be nearing what developed countries consume on average. I think 40M to even over 45M cars in the Chinese domestic market is actually not unreasonable.
Remember, China bought 26M cars in 2023 on a per capita income of $12500. And that is an bad year beset by RE unwinding, trade wars and Covid vestiges. By 2030, the projection from PwC is over $20000 for per capita income while others have $18000 on the low end.
The US market at 16M in 2023 won't be growing much larger.
Just holding a dominant position in China with Toyota wiped out from there can give BYD or any other Chinese firm the top spot without the US market.
According to projections by the Society of Automotive Engineering of China, the country’s car sales in 2030 will be 38 million, of which the sales of EVs will be 15 million, or 40%.