Don't forget one thing, 7D has new firmware and that might improve the IQ bit. Unfortunately, I have not chance to test the new firmware out.
That's not really gonna improve IQ, as it doesn't affect the sensor or how the image is written. Maybe if you shoot all .jpg it could help a little with how it processes it, but for RAW files, Id be stunned if there is a difference. It was more an improvement on burst rate and some video features.
Having used the T2i, T3i, and 60D, the IQ is the same in all of them if I was shooting the same scene. Haven't used the 7D, but I can't see why it would differ