While you could never really test 3 Million people being online at the same time I also hope there prepared because all hell will break loose..LOL I had read on some site in Mid Sept and they posted stats on MW2 and there were still 400,000 players online that's almost 1 year later so I hope TREYARCH is prepared.
If these guys are smart unlike infinity ward they will estimate about how many will be online and add 50% of what there estimate was. If not then I'll just play the campaign. Didn't the server crash for mw2 and WaW on release for ps3? My friends always used that as an excuse that xbox was better.