Should be fine on high, even with some settings on ultra if you OC. My unlocked/OC 6950 runs with everything on ulra except MSAA and motion blur @ 50+fps on avg. @ 1080. Deffinately OC that card though as it will be worth a few fps for sure!
A single 560Ti is a bit faster than my 4870 CFX setup from some of the benches I've seen and I run on High + some Ultra settings (so a custom template really) and have no problems getting 60+FPS average.
I have the EVGA 560Ti paired with the Core i5 2500k, and I run BF3 with everything on Ultra but shadows (Medium) and AA off. I average at least 50+ FPS. Even on Caspian Border 64 player match (which seems to be the most taxing on MP).