The Mercenaries mode, revealed last week, was set to only support co-op play offline, but IGN report that there's already an update on Xbox 360 that adds online co-op play to the forthcoming game.
Capcom apparently didn't respond to questions regarding the patch, but IGN have confirmed that the patch exists and works on their copy of the game.
There's no confirmation of a PS3 patch yet.
Watch my screenshots trailer here... please subscribe