InXile Entertainment are taking notes from Larian apparently since Wasteland 3 will feature co-op multiplayer after the latter's turn-based RPG series, Divinity: Original Sin, successfully integrated the feature. It has no PvP though.
Wasteland 3 has been moved from 2019 release to Spring 2020 as Brian Fargo and the rest of inXile wanted more time to polish things out and wrap up the work on certain features. For example, more animations will be added for better visual fidelity and multiplayer will be fleshed out.
In the case of multiplayer, Wasteland 3 will support two-player co-op and it will have a few quirks since this is a turn-based game. Those familiar with Wasteland series will remember the previous instalments had the player assemble a party of Rangers, which will persist in the upcoming game.
However, if playing with a friend, they will need to split control of the group so each player gets the same number of units to control. The full party will have up to six characters, meaning each player will get three characters to control.
Each player will be able to interact with the world so it's possible they will coordinate with each other when making decisions but should one decide to make a choice that doesn't fit the other player, they will have to live with it.
To prevent unwanted story branching and world evolution, players will be able to rely on the invite-only method of acquiring teammates so it's less likely a friend will purposely attempt to make a choice that would affect your game in a negative way.
If they do, however, there will be another contingency in place. Multiplayer sessions will be instanced so if one player is extremely dissatisfied with the way the other player interacted with the world, they can simply go back to their singleplayer session and make the choice they like.
Furthermore, players will not be able to actively engage in PvP, it is all in the spirit of co-op. Brian Fargo and Tim Campbell didn't talk much more about it with so we don't know whether friendly fire will remain in the game since it's not hard to line up a shot that has a chance to hit a teammate for a rudimentary form of PvP.