Toslink can't handle the bandwidth of a DD+, DTS-HD, or Dolby TrueHD bitstream - the signal's too big. TrueHD in particular involves a lot of data. You'd need to somehow process the bitstream first (perhaps decoding it to PCM as required with HDMI 1.1/1.2 and then passing it across three or four toslink connections), and that is just too ungainly to be widely accepted. Firewire could probably do it (haven't seen the numbers actually run to verify it), assuming anyone establishing the standards wanted to give it the chance to. I'll let others decide how likely that is.