A leak online seems to indicate that multiplayer downloadable content for Mass Effect 3 is on the way and will introduce new playable races to the mode.
A screenshot posted over on Reddit shows one of the booster packs that can be bought to up your multiplayer options and features new classes getting unlocked. There's a Batarian Soldier and Sentinel, a Geth Engineer and Infiltrator, a Krogan Battlemaster and an Asari Justicar.
The last two classes will likely be similar to two of the core Mass Effect cast - Wrex is a Battlemaster and Samara is a Justicar. Speculation hints that these unlocks may be related to upcoming Mass Effect action figures.
We've been told - and believe - that a Mass Effect 3 multiplayer map pack is incoming and will be called the "Resurgence" pack.