From Spotify staff:
"Spotify for Windows Phone has been placed into maintenance mode. Thus, we will only be making critical security updates to the current Spotify app and not releasing any new features nor improving support for old devices going forward. Users can continue to use Spotify on previously supported Windows Phones and Spotify will remain on the Windows Store.
We will continue to work closely with Microsoft to ensure the best experience on Windows platforms and are constantly evaluating the most effective path going forward."