Horizon 3 went Gold a few hours ago, because of this the developers released a full Xbox Live achievements list, the recommend PC specs (below) and a new vehicle that was added to the game, the 2554 AMG Transport Dynamics M12S Warthog CST (below):
The developers just released a blog post about some of the vehicles that are going to be in the game, you can read it here. The most interesting thing that I saw in that post was that the game is going to feature more than 350 vehicles, which is 150 more vehicles than Horizon 2.
They also showed a few new screenshots showing some of the new vehicles, I have to say that they are looking really nice and they fit the map of the game really well! The graphics of the game also look insane (if those are the final graphics)!
There's a little bit of Horizon 3 footage starting from 0:57 in the trailer. The trailer was made to show off the "Summer Car Pack" DLC for Forza 6 but they included a little bit of footage from Horizon 3 as well to show off the new Cadillac CTS-V Sedan