The general intention for Android apps is for a single app to work across both mobile and tablet form factor without the need for separate apps - much like Gmail which shown split panes when on a tablet screen.
However, more support is definitely needed for Android tablets - at the moment they won't even stay online if you try to sync some playlists and don't have a 3G model.
Spotify will not comment on development plans or release dates though - so you're stuck with the rest of us waiting - there's not even an official app to support Android 4 yet (although you can download a beta) so we could be waiting a long while until Spotify realise that there's more to life than an iOS fixation.
---------------- Listening on Windows, Android and Sonos. Tweeting it at @davelicence