You're not fooling anyone. We know Mass Effect 3's going to have a multiplayer component of kinds. You may as well just announce it.
It's pretty much confirmed anyway. A scan of a South African magazine lists the contents of a Mass Effect 3 collector's edition, with a "multiplayer pass" being amongst the goods.
Rumours suggest that the upcoming sequel includes a standalone online co-operative mode that includes elements of competition. Presumably it will involve shooting stuff. Because Mass Effect has always been such an awesome shooter.