ORD for Shuttle is fairly senior. There is also about zero growth occurring on the Shuttle side of things although that could all change tomorrow (the rumor is something about 175's for Delta which would cause a lot of movement around Shuttle). Everyone that gets hired on at Shuttle is being hired due to attrition and there is v-e-r-y little movement going on there. I personally can't remember the last time a Shuttle upgrade class was announced.

P.S. - When they call you for class they will tell you what certificate and airframe your on. That determines what bases you can get. You don't really get your base until around the time your start sims.