As things stand, Spotify seems to be discontinuing Squeezebox support soon (this month) and is sending out emails about this.
There is, however, a pretty good workaround, at least if you use Logitech Media Server (version 7.7.x and newer, 7.9.1 recommended), the new “Spotty” plugin:
If you currently don’t run your own Logitech Media Server, you might consider using a Raspberry Pi for this, it will probably give you better performance for your Squeezebox system than MySqueezebox.com alone, consumes little power and there are ready-made distributions for Squeezebox available, like Max2Play or piCorePlayer.
And then just go on listening to good music!
You can find more information about the Spotify discontinuation here:
And directly from Spotify: