I think digital amps will certainly have matured to the point where they could compete with some of the very best today - offering incredible dynamics and (hopefully) not sound thin or lifeless sound during low listening volumes.
It seems if Blu-ray or DVD-HD replaces the DVD of today, there would be similar technology at use in music playback so one player would be able to handle music or movies (or the integration of both).
Speakers will be limited by the laws of physics, which has been pointed out, but perhaps will incorporate several technologies. As gmarcotte mentioned, filters may be good enough, spohisticated enough and small enough to send different frequencies to different parts of a speaker. For example, low frequencies to a sub, highs to a ribbon and everything else to an electrostatic panel. Using a "room optimizer" of some sort would help integrate all of these different sounds and eliminate phase problems, etc.
The "high speed" cables I was thinking about would be used to carry a signal from source to pre then through the above mentioned crossover, direct to the digital amp. Only from that point on would we see traditional wire. I think HQ wireless sound on par with today's finest wire is more like 20+ years away. Using this type of connection should/could eliminate many of the challenges inherent with current cable design.
I'm just guessing of course, but anything that would increase the realism of the sound and picture, add extra convenience and reduce the size/quantity of the equipment is progress in my book.