It appears as though players will be able to get their hands on several new Mass Effect 3 Co-Op missions in the very near future.
There's a Reddit post that leaks the following summary:
"The day of reckoning is nigh! The Reckoning Multiplayer Expansion brings six new never before seen co-op story missions to the game and new co-op gameplay modes. It provides four new maps to conquer and hazard variations of the Earth maps. It also enables reinforcement packs that offer new kits for the salarians, krogans, humans and volus. In-game reinforcement packs now include three new weapons (Chakram Launcher, Blood Pack Punisher and Adas Anti-Synthetic Rifle)."
Additionally, there's been a datamine leak that discusses the game’s new multiplayer modes.
This is in addition to the upcoming single player DLC as well. So it looks like it's a good time to be a Mass Effect fan.