My understanding of the thing was - it never had enough volume to justify doing the system integration work properly, but was complex enough it required at least one full time cast member making sure WDW and DLR's incompatible systems were in sync.
The need for park reservations and the growing divergence in benefits between the Magic Key product and the WDW AP makes that exponentially worse.
I can't see them bringing it back unless kicking and screaming. They just won't introduce a new product that needs to be sold in person.
They'd rather focus on useful things, like being able to update your credit card for your monthly payments online (seriously, you still have to call).