I personally feel the BF3 is going to be the better game out of it and CoD coming out this year, but CoD will still keep its top place simply because people have played it before and go 'OMG CoD!'
If BF3 does take over, for me this would be a great satisfaction, and a great disappointment. The Satisfaction would come from having CoD dethroned, and having the better game take its place. That and the fact that one of the 'will sell well no matter what' games will have been bought down to your average game's level, which is IMHO where it belongs.
The Disappointment would be that the Battlefield community would become even more flooded with hackers and young gamers who find it acceptable to scream obsenities into the microphone who would have to come from the CoD fanbase if BF3 did hypothetically become more popular than CoD.
For the industry, this would hopefully encourage:
a) Developers to break the bounds of what we know games are, and come up with new ideas rather than copy CoD (Though they will likely just copy BF3)
b) Developers to develope for the PC first, then downscale the game for consoles rather then creating the game for consoles then adding stuff on top for PC (The BF3 team has stated that them doing this has improved the game for both PC and Console)