Uh, I don't think so. Any so-called capital gain would be on the specific asset, in this case, the car currently worth $50k. Now, I'm betting the ranch that the original cost of that car was more than $50k, so there is not gain -- its a loss. For example if the current car originally cost $65k, but is now worth $50k for a trade-in, the loss is $15k.
OTOH, if the $50k car is a collectors item and originally cost $40k, there would be a $10k gain on the appreciation. But appreciating assets are only in Elon's dreams.
Again, the fact that you are trading in one asset for another like asset does not move the federal cost basis over -- it stays with the original asset, in this case, the $50k car.