I think many 717 pilots are playing the waiting game on the 737, and not bidding over in the beginning. They are wating to see what the schedules look like, and until more aircraft are on the property so that there is more variety and see how the dust settles. Just like is the case when any new aircraft first appears on the property of any airline.
So, just because there are very few 717 pilots bidding over on the inititial bid, does not necessarily mean that will always be the case. I think a significant number will bid over once there are a suitable number of aircraft on the property, and the schedules are more of a known factor. There are simply too many unknowns regarding the 737 right now, so no one is bidding it. This wll change with time, so it could very well be that new hires into the 737 could be junior for some time to come. You never know what will happen until it happens....