I've been a user for some years now and it would be cool to hear higher bit rates in every audio codec form as it would be nice to hear it in ear-pleasing form at full resolution in both compressed and uncompressed formats as other audio competitors offer high quality audio streaming as it adds dynamic depth to the music.
Furthermore, it would be cool to introduce a video upload feature. Now I know SoundCloud isn't YouTube or Vimeo by any means but just to try it out in beta to see if users would react positivity or negatively to the idea. The video upload function would serve a purpose in a music perspective for music videos for new artists as well as podcasters. If you're concerned about bandwidth, you can stream it at 720p HD instead of 1080p Full HD since a lot cameras can record 720p. If artists upload UHD/Full HD video content, SoundCloud would automatically downgrade the resolution at 720p to SoundCloud's custom or new upcoming codecs for best streaming, visual/sound quality, and buffering times.
Again, these are just ideas but in my opinion, I think it's just something to think about and hopefully my ideas will be considered sometime in the future.