I think it's fair to say that they are going to lose a chunk of current season ticket holders whatever price they come up with.
With that in mind, maybe they need to get away from the idea of early bird renewals, and just have early bird prices open to all. The only way this club can start to grow again is to get 'new' people through the door, they can't rely on the current season ticket holders all the time.
They've made this mistake for the past few years. The renewal prices have been great if you've already got a season ticket, but there was little incentive for people who didn't currently have an ST.