In simple terms, players who purchase either the Xbox 360 version or the PlayStation version of Destiny will be able to upgrade to a new console in the future at no cost. Many developers have provided discounted 'upgrade' promotions that usually allow a player to purchase a PS4 or Xbox One copy of a game for a discounted price, as long as they own the same game for either the PS3 or Xbox 360 respectively. This is the first time a developer has offered a game upgrade for free, which is pretty awesome.
There are a few rules to the free Destiny promotion - firstly, players must choose to upgrade before January 2015, as the promotion will end after this period, and secondly, players will only be given a digital version of the game to download from either the Xbox Games store or the PSN marketplace.
Players will also only be able to use the promotion within the same console family. For example, PS3 players will only be able to grab a free version for the PS4, and Xbox 360 players will only be able to grab a free version for the Xbox One.
Finally, players who upgrade will be able to carry their stats over to their new console as long as they use the same gamer profile for both consoles.