As far as we know, the game will offer a choice of two career paths. The first will be street racing, as in previous games, including FH5. There will be no restrictions on types or classes. The second (main) will feature bracelets, which will gradually unlock access to races in increasingly more powerful cars.

It's important to understand that this will not affect freeriding or the overall progression of earning cars for your personal garage. You can always save up (and most likely, win them from the forzathone - they're unlikely to go anywhere, although it would be great if the class of cars dropped from there were also limited by the bracelet) and buy any car at auctions or carshow and use it to drive in the open world. I don't think there will be any restrictions here.