Grand Theft Auto V, which will have 700 missions alone. For starters, almost anything the player can do in single player can be done in GTA Online. The Social Club will host the Online servers.
According to the interview, "the camera will zoom out and pan away to your online character seamlessly. During the animation, a matchmaking process will be in progress" and "matchmaking will depend on which friends are playing, and what people have ranks near yours."
Missions will be randomly assigned, and will have a ranking - naturally, the higher the rank, the harder it is. Certain missions will require certain weapons, vehicles or character types such as snipers or drivers. Missions can be so complex players will really need to coordinate to complete them. Player-created missions can be downloaded from the Social Club. Players can even watch races and deathmatches in process from their crib's TV.
In missions, players will have something called "team lives" - if a player dies, a team life will tick off, so any combination of that number of deaths in the team will fail the mission.
Grand Theft Auto V will be released on the 17th September 2013 for Xbox 360 and PlayStation 3. The PC version is unannounced.