Some of the team from Project Reality for BF2 are now working on BF3 at DICE/EA's request as they managed to get 128 player games working on BF2 where the devs had failed.
Source - http://www.realitymod.com/#Among the various tasks these people will be working on is implementation 128 player support on PC, as well as modification tools and scripts. Although previously announced that Battlefield 3 will be limited to 64 players on PC, and modification tools were unlikely, while true when announced, this acquisition has given DICE the opportunity to explore and develop these areas of the game before BF3 ships.