Fallout is one of those series where people never begged for multiplayer. It was more like “Wouldn't it be cool if Fallout had multiplayer?” Well, game director Todd Howard for the upcoming Fallout 4 was thinking the exact same thing, but came away convinced multiplayer wasn't right for the experience.
Mashable managed to get in a word with Todd Howard who talked up the possibility of multiplayer in a game like Fallout 4, where he explained...
Believe it or not, every time we do a game we design a multiplayer mode just to see what we would do, […] Then we go, 'Yup, we shouldn't do that. That's an awesome idea that is way too distracting from the main thing we want to do, which is single player,'
This is one of the most reasonable responses regarding the development of a game I've ever had the pleasure of reading. Howard directly notes that they tested multiplayer beforehand but he's acknowledging it just doesn't fit. It's definitely better than a canned PR response that feels like a dodge rather than an admission that creatively maybe multiplayer just doesn't work for the game.
Fallout 4 seemed like the kind of game where multiplayer would just break things. A lot of it is centered around player choices and explorations that affect the world at large. From a design point of view I don't know how they would implement multiplayer where both players still maintain their agency. The only thing they could do is something like GTA: San Andreas' Rampage Mode, but I tend to doubt that gamers would really appreciate being attached to the hip of another player.
That's not to say that someone won't make a multiplayer mod at some point for Fallout 4, because many times that has happened for other popular games. For instance, Just Cause 2 managed to get a multiplayer mod that enabled thousands of players to join in on the fun and play the traditional single-player title with lots of other players. A multiplayer mod was also being worked on United Front Games' Sleeping Dogs. It wouldn't be surprising if Fallout 4 joined them at some point.
For now, Bethesda is working hard on bringing the open-world, post-apocalyptic game to life for home consoles and PC this fall.
The company has previously confirmed that mods will be made available for Fallout 4 starting in early 2016 on the Xbox One, and if Sony gives them the go-ahead they'll also bring the feature to the PlayStation 4 as well. So, once again, if someone is able to make a mulitplayer mod and it appears on consoles I don't think anyone would complain too much.
For now, the fourth canonical entry in the Fallout series is shaping up to be one of the biggest releases this fall with a huge blockbuster sales expectancy to follow. I tend to doubt this is one of those games where the lack of multiplayer is going to have people canceling pre-orders or claiming that the game is now dead to them.