Something that likely means nothing, but in some of the conversations you can have at the Café the people sometimes reference other cars not in the game.
There was one that stood out to me at the time though, when you speak to Jeremy with the BMW McLaren F1 Gr.2, in which he says at the end:
"Two years later, BMW settled the score in a way with its own Le Mans victory!
But that's a story for another time."
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Foreshadowing the return of the BMW V12 LMR perhaps? It hasn't happened yet if it is. Like I say most of these references to cars not in the game are going to be unrelated to future content, but this one in particular stands out, to me at least.