Even if multiplayer was the last thing you wanted or needed from Bioware's Mass Effect franchise, it looks like it could be on the way for the trilogy closer, Mass Effect 3.
This all comes from a scan of a South African magazine, which contains an ad for the Mass Effect 3 Collector's Edition. One of the items listed is an "online multiplayer pass."
The inclusion of a "pass"—which EA uses as a means to combat used games sales, since you either need the code that comes with the game, or to fork out $10 for an individual pass—hints at something more than the already-announced co-op play. Here's the ad in question:
Bioware expressed interest in exploring multiplayer when asked about it in the past, so we'll have to see if that's part of its Mass Effect-related announcement set to come later this month.