AT&T will release a patch that only unmodified Nook's can receive. Devices without the patch won't be allowed access to the network.
Then Nook dev's will circumvent it and the cycle will go on.
I think AT&T should just offer a non contract 15-20 dollar a month solution and unlock the network on all of them. This is a fight they can't win, as everything in the Nook's software is open source and fairly easy to modify. I know I'd shell out $200 a year for my daughter to have complete data on her Nook (when we ever get it!) vs. me having to monkey with the software every time AT&T releases a patch.