People never should have taken those comments about Mark Prior as seriously as they did. That is because they were made by Tom House, who had a gigantic conflict of interest because he was the person who taught Mark Prior his pitching mechanics.
I don't think House has completely retracted these comments, or at least his followers haven't.
You still hear a lot of "wait til next year" things being said about Mark Prior by House boosters like Will Carroll and Carlos Gomez.
I don't see Mark Prior amounting to much in the long term (or even the short term) until and unless he rebuilds his mechanics from the ground up.