You are always taking a gamble at paying a higher price if you wait but I think I'd wait and see how the season plays out. I'd say at most you'll pay $30 or so over face if the Bengals and Cowboys are playing well by week 14. In all my years of holding season tickets I very rarely made a huge profit selling and if I did the opponent would be the Steelers or Browns. For one game I think I'd look for club seats but it'll be cold on the East side in December.
If the Bengals aren't playing well, you'll be able to find tickets at or below face value.
With their schedule, I think the Bengals should have a pretty decent start to the season (4-2 or so).
Either way, your best bet is to wait right now. Very few season ticket holders are willing to sell their tickets for face value at this point because the value could increase with a good start to the season.