While MagicBands certainly still work, and the official announcement from Disney on MagicMobile is sure to point out that the resort hasn’t given up on them yet, the decision to let guests use their smart devices instead of a MagicBand follows on the decision to no longer give MagicBands to resort guests for free.
On the plus side, I guess it’s nice that the Apple Watch will give you this functionality, as that means it will essentially still work like a MagicBand, just the world’s most expensive MagicBand.
It was an easy way to get people to use the device, and potentially buy more of them in different designs, but now there’s much less incentive to use MagicBands, and it seems likely that they’ll be phased out entirely at some point.