Second Son Doesn't Have Multiplayer
Not every game in existence requires multiplayer.
While we've heard rumors that Sucker Punch's inFamous: Second Son will feature a multiplayer option of some kind, the official confirmation is simple: No.
According to UDN reporting on the Taipei Game Show (as cited by DualShockers), Brand Development Director Ken Schramm has clarified that Second Son doesn't have multiplayer "in the game's design." Personally, I'm now even more excited for the game, because it means the developer spent 100% of its time and resources on creating an awesome campaign.
Schramm dished out a few other intriguing details; for instance, players will be able to tackle optional quests (common in open-world sandbox experiences), but we'll need to be careful. Choosing good or evil means certain situations will be "irremediably lost," which forces us to think before acting. This isn't new, though; we had that mechanic in the previous inFamous entry.
Lastly, the main character, Delsin, won't be able to use different elements at the same time. He'll be able to use smoke and neon (and a few others we don't know about yet), but each element will have a meter. Presumably, when that meter runs dry, you'll have to either replenish or switch to a different power.
Multiplayer isn't a deal-breaker for this game
I know everyone these days thinks a video game needs multiplayer. I've never believed that. In the case of Second Son, I'd only view it as a potential asset, and an unnecessary one at that. Besides, even if it did offer multiplayer, who's buying it specifically for that reason?