Bungie has emphasized that the universe of Destiny will be "alive." Events may happen in-game that are not necessarily controlled or planned by the developer, which will help to create a dynamic developing experience for Bungie and a dynamic playing experience for gamers. The game's style has been described as an always-online first-person shooter that will incorporate massively multiplayer online game (MMO) elements, but Bungie has avoided defining Destiny as being in-kind with traditional MMO games. Instead, the game has been referred to as a "shared-world shooter," as it lacks many of the characteristics of a traditional MMO game. For instance, unlike many MMO games — particularly massively multiplayer online role-playing games — players will not be able to choose from a number of different species for their character, but instead will be limited to playing as a human. Additionally, rather than players being able to see and interact with all other players in the game or on a particular server (like a traditional MMO game), Destiny will include on-the-fly matchmaking that will allow players to see and interact only with other players with whom they are "matched" by the game.

I actually think they're considering it to be a game changer, there is a lot of talk that it doesn't really definitively fit into one genre of game. As for the release date I'm not sure on what you're expecting from a release date, any release date given now would most likely be changed, we have no idea how far into production this game is.