This will be available in version 6.1 of ACR which will be an update to the shipped version (6.0) of ACR that comes with CS5. Also part of LR3 when it comes out later this year.
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Lens Correction Video
Camera Raw 6 and Lightroom 3 Lens Correction Feature Preview
This will be available in version 6.1 of ACR which will be an update to the shipped version (6.0) of ACR that comes with CS5. Also part of LR3 when it comes out later this year.