Yes, multiplayer is returning.
Multiplayer will be making its return in Mass Effect Andromeda, according to Game Informer (via NeoGAF)- and it will be a more refined form of the multiplayer in Mass Effect 3. The game will, like so many other multiplayer games, have a card based economy, with players earning XP and credits. It will also have microtransactions, though Bioware insist that no real world money is required, and players can play through the multiplayer simply by earning credits in game.
Multiplayer games will allow you to customize their conditions- so, for instance, you can set a game so you take more damage, which will net you higher rewards if you win, or you can set it so you dish out more damage, which will lead to lower rewards- it’s actually a bit like the system in Kid Icarus Uprising and Super Smash Bros. Bioware also plans to release custom crafted missions with unique modifiers that players will not be able to change themselves. These custom missions will give you ‘Mission Points,’ a unique currency that can be used to directly purchase items and weapons, instead of having to purchase random cards and packs. That said, listings of these items and weapons on the shop will have very short turnovers, so you’ll want to act fast.
Unlike Mass Effect 3, the multiplayer will not influence the ending of the single player game, though Bioware do admit that playing multiplayer can have advantages for the single player game. Bioware are also adding a new Prestige mechanic- with several types of characters, you can earn Prestige XP in addition to regular XP. Earning enough Prestige XP extends the benefits that character enjoys to other characters too.
Mass Effect Andromeda will launch on PS4, Xbox One, and PC.