Digby is also in a limited bundle in Japan, while sold individually, Isabelle is also sold individually there too. They'll highly likely release Digby and Isabelle alone like they did there, it's just a matter of time, probably into 2016 after the holiday rush so people bought the higher priced combo instead of just 1 or 2 amiibo- they're a business after all, trying to make money off this amiibo craze.