Major hotel chains like Hilton are implementing mobile phone room keys, so it's not beyond the realm of possibility for DLR.
The issue is ROI. MagicBands and associated infrastructure cost WDW well over $2 billion with the promise of an astronomical increase in guest spending as a result to make up for the cost. It's been 4 years now, and that astronomical increase has not materialized. While the cost to implement at DLR would be less, no one is in a hurry to do so due to the lack of positive results at WDW. WDW has a much higher ratio of multi-day tourists to locals/APs than DLR.
Could it happen? Of course. Will it? Probably not. The drive is to invest in actual resort needs, like capacity (attractions) and infrastructure (parking), which is fine. Those needs are urgent. MagicBands are not.