Disneyland should be next. With the massive AP base there it seems like they'd be the easiest to role out to next. That would get a nice chunk of the people on Magic Band.
Disneyland Paris is nice too, as it has the large resort hotel occupancy which means that many of their guests will be eligible for Magic Bands.
Tokyo Disney and Hong Kong Disney I'm not as sure about on this front. Do they have large installed Annual Pass bases? Tokyo does have 3 Disney branded hotels on property. Hong Kong is following suit. Not as many hotel rooms as WDW and DLP. Even without Magic Bands My Magic is still better.