In a recent blog post on the Forza Motorsport website, Microsoft and Turn 10 have announced that Forza Horizon 2 with all of its DLC packs will be removed from sale in September.
Presumably this has come about because of expiring music and car licenses. After the 30th of September, it will be removed from sale, but those of you who have already purchased the game will still be able to download it.
Forza Horizon 2 is currently available for free as part of the Games with Gold promotion, so if you want it, now would be a pretty good time to add it to your collection.
Forza Horizon 2 originally launched on 30th September, 2014. The newest game in the Horizon series, Forza Horizon 4, launches on the 2nd of October.