Firstly, why?
A "moderately known YouTuber" once put together a list of 20 cars he was absolutely positively sure were coming to GT Sport in the next couple of months. He actually named more than 30 cars and even then only got eight right... over two years.
It's not simply more right because there's more cars in it...
... but more importantly, vehicle names being in game files is not the same thing as vehicles being in game - as with the Porsche I mentioned. There's no particular reason to suppose that players will get hold of all of, or indeed any of, those cars just because their names are marked somewhere in game files.
It's certainly an interesting discovery (if verifiable), but it's not "leaked upcoming cars".