Isn't Apple wholeheartedly supporting wireless n? Isn't that a "good enough" equivalent to ethernet?
And on a different subject: What are your views on a TosLink or other S/PDIF port?
Having just HDMI assumes the user has either a central audio/video switching receiver with HDMI, or that their TV has an HDMI or other digital audio output to feed the big sound system.
I don't know if either of these assumptions applies to a large enough demographic (but very likely, Apple knows better than I do). I also wonder if Joe VHS will be able to even set it up in a way that it works to give the best UX. Likely many will just be plugged into the TV via HDMI, to be enjoyed with TV speakers instead of 5.1 channel sound.
This home theater setup stuff is complicated with many old formats still in use - heck, Apple provides a VGA adaptor for the brand new iPad! I wonder how many people use Component with TOSLINK/S/PDIF instead of HDMI.