I think ISU has been recruiting better talent, especially at WR and OL, and I think it will start to show up in the next couple of seasons. It's just that the upgrade in talent is incremental so it's not like freshman are going to come in and beat out seasoned, but less talented, seniors.
Using BCS offers as a measure, ISU's starting OL has a combined 0 non-ISU BCS offers between them. The starting WRs have 1, I think. I think Dika, Williams, Burton, etc. have a potential to pass some of the other guys on the depth chart and upgrade the OL along with a more experienced Farniok and Gannon. Same with the freshman WRs.
Same thing on the defensive end. McDonough, Laing, Scott, Maggitt, etc. are good players, but the young D-lineman appear to have more raw talent -- but they aren't the kind of blue-chippers that are going to beat out seasoned, but less-talented juniors seniors. Cousins, Bevins, Rogers, Brackens, Lawry, Aka are all guys that have potential to upgrade talent level at some spots. They won't come in as freshman and blow you away, but they will eventually provide upgrades.