Various Fallout games, from the very first one to Fallout 4, have always been singleplayer affairs with players only having their companions as another person around as they wander the wasteland in each game. According to Todd Howard, Fallout 76 will cover an enormous area, and it will be four times the size of the earlier game, Fallout 4.
Howard explained, in regards to Fallout 76: "We would have loved [cross-platform] with Fallout 76 but right now we can't". Epic Games revealed the launch at E3 2018, and Sony received heavy criticism for their decision as it cast a massive shadow over the whole release.
Sony is in a tough spot as Cross Play is tied to more than just pure gaming entertainment for the company, a lot of factors such as in-game purchasing, security, and licensing would all impact the platform. It's different, but if you sit down and play it you would recognize it as something we made, if that makes sense? This has most recently drawn the ire of fans around the world who became aware that Sony was preventing PS4 players from joining their friends in matches of smash hit Fortnite on other platforms. On Wednesday, PlayStation America CEO Shawn Layden said that Sony is "looking at a lot of the possibilities", but didn't make any promises. Competitors Microsoft and Nintendo are allowing it in certain titles like "Fortnite", "Rocket League", and "Minecraft", but Sony refuses to participate.
As battle cries go, "Sony is not as helpful as anyone would like", does not sound like an authoritative and ringing declaration that immediately betokens the collapse of a lock-in empire. In Fallout 76 servers will be filled with dozens of players and the map is very big so you wouldn't meet a player at all time. Among other questions, he had been asked about if the upcoming survival Fallout 76 would support a crossplay between PC and consoles.
A few days ago Todd Howard had an interview to clear up the things regarding the cross-platform play in Fallout 76.