This is up to radeon and nvidia respectively. They usually won't do any optimising for sli or crossfire until the game is released. I'm not this computer savvy; I read it somewhere couple of months ago.
If you have geforce cards I think it's possible to force sli. Some guy on YouTube helped me but wasn't sure how to check If it worked so I bought a new card.
nvidia and ati will release new drivers when PA is released (or won't) get new drivers then. Be warned though. sli and crossfire is not the way the future is headed, apperently the hardwarce devellopers want to go back to having all the power in a single card.