Audi will be dominant, just like Ferrari will win about everything in Formula 1.
They've got the best drivers, and the best chassis. Champion Racing, which ran a 2001 spec R8 last year, without any factory support, was still faster than Cadillac, Panoz, MG and the rest of the LMP900s, and you can expect them to be a force to reckon with this year again.
Besides, Bentley is now owned by Volkswagen, which owns Audi, Porsche, Lamborghini, SEAT, Skoda and whatever else... Even if the R8 isn't dominant, and the Bentley is, they don't care whatsoever, they're still winning in the end!
I expect Joest to take the ALMS championship again this year, and probably Le Mans too.