I am psyched for this, and I will probably get it, but...
Battlefield 3 will probably not knock off COD from it's pedestal as the number one FPS. Why? Because most games with great graphics aren't always the best games. Take Crysis 2 for example. It had amazing graphics; the best I have seen, and I was nearly ready to jump the gun and buy it. But not many people play the multiplayer or the game, unlike COD. COD is the game you play because you want to have fun in a short amount of time. The reason why it's so easy to latch onto is because of the easy control scheme, and it doesn't take a team of six people to beat another team of six people. It's simple mechanics and simple thinking. Battlefield puts vehicles and other things of that nature in, but as that might be what we're looking for, we won't get hooked to it like COD.
Think about this. 470,000 people were playing COD as of a few hours ago on the Xbox just alone. I bet you the number of people playing BFBC2 combined is far less than that of just the Xbox alone. It's probably because a lot of people can play a lot of matches of Black Ops in one hour than you do in BFBC2. To beat COD at their own game, they need to include more than what COD is offering and include the same type of gameplay. Bigger maps aren't always better. It means you'll have to travel more to kill your enemy, it means you'll waste more time trying to win one game, which is probably why less people play it.
It might be a great game, but if it takes more than twenty minutes to complete through one match, nobody wants to spend that much time to do so. Especially with a team of people who are highly trained to work together. Don't get me wrong, I might go for it and play it. They probably won't sell as many copies as the next COD installment though.