Quick list in mostly no particular order :

• cleaner and modular internal handling of the playlist
  • will allow pluggable play-mode like an album-mode that play whole albums
• change internal handling of tags (separation between the storage and the usage, using keywords for the usage) (done in v1.1.x)
  • will allow changing/translating the <Unknown> for unknown artist/album
  • will allow better support for multiple album with a common name
  • easier to add tags (in progress)
• artist/album pictures
  • more cover/artist picture options : to set default load/save folder/filename
  • more than one picture
  • cover manager
• lyrics
  • more sources for lyrics :
    • using the ruby amarok script http://lyriki.com/Help:Wiki-Lyrics_Script ?
    • http://lyrics.mirkforce.net/cgi-bin/stats.cgi?period=1 ?
    • support for reading/saving the lyrics in the lyrics tag
• SongTree
  • implement playlist/list/queue mode (done in v1.1.x)
  • implement type-ahead search (done in v1.1.x)
  • implement column drag-and-drop
  • better grouping modes (partly done in v1.1.x)
  • add a way to define actions to execute based on where the SongTree is clicked on
  • some optimizations
• custom filename pattern in autofill mass tagging (done in git)
• better genre edit widget in masstagging (that allow removing a genre from all songs without touching the other genres) (done in v1.1.x)
• options to save lastplayed, playcount, rating, labels, lastskipped and skipcount in tags
• FPane tree like for example genre → artist → album (→ songs)? (done in v1.1.x with some minor bugs, no →songs for now)
• ipod (probably after creating perl bindings for libgpod)
• web radio
• lastfm neighborhood “radios” (less likely now that last.fm streaming is only available in a few countries)
• support for m4a and wma (support for m4a in git (not well tested yet, please use backups))
• support for cuesheets
• fix expandbox inside a paned
• asynchronous DNS request in simple_http.pm (done in git, use either wget or AnyEvent::HTTP)
• more widgets
  • next song (possible v1.1.2+, by using the group option : Title(group=Next) (see this commit))
  • list of songs from album (in progress)
• change contexts and ExtraWidgets system (done in v1.1.2+)
• gui layout edition
• composite layout widgets. example : defining a widget composed of the Prev Stop Play Next buttons, that can be re-used in multiple layouts, so removing the Stop button from this composite-widget would affect all the layouts using it. (possible in v1.1.2+)
• change the “timeslider” so that the handle is smaller, and replace “click-to-scroll” by “click-to-jump” (done in v1.1.x)
• a way to set an arbitrary position for the “traytip” on song change, and make it possible without a trayicon
• way to configure context menu's web link (AMG/google…) (in a plugin ?)
• configure the context-menus ?
• add option to show empty or custom picture instead of nothing when no artist/album picture (almost done in v1.1.x : lacks GUI)
• playlist history (to correct mistakes,…)
• use SongTree drawing code (“graphical elements”) in Mosaic mode, in a layout widget ?
• replace all the %letter syntax by the much more powerful, not finished, new syntax (in progress, can already use $field in v1.1.x)
• add replay-gain song properties (done in v1.1.2+)
• equalizer :
  • support the equalizer option in mplayer (although it can't be change during the song)
  • allow loading/saving preset (the band frequencies in the gstreamer plugin and the mplayer option are different → I'm not sure what I should do)
    • <ochosi>: mplayer and gstreamer use two different models (preferred and calculated center), the difference between the two could be considered as redundant. (source)
• better “album menu” to select songs from album with album picture
• way to select songs of a SongList/SongTree based on a filter
• option to separate artist/album with less than n songs in the artist/album menu (already done but no GUI to activate it)
• make using mpg123 instead of mpg321 possible. (done in v1.1.x)
• redesign copy/move/mass rename actions
• webcontext : open link in other tab / right-click menu
• alternate size calculations modes for cloud view (based on number of songs played …) (some modes are possible in v1.1.2+)
• button to select a colored square/shape as a label icon