I don't think it was the MP3 format per se that killed high res audio. Rather, it was the way people listen to music now. Of course, there are still people who will sit down in front of a pair of high end audio speakers to listen to an album. My sense though is that, for most people now, music is the soundtrack to their lives. Music is in the background while we do other things (work, walk, exercise, etc.). The portability of the MP3 format dovetails perfectly with music always on in the background.
There are two main problems with higher resolution formats gaining traction: education and high cost of entry. Regarding education, the details of sampling rates and bit depth are beyond a lot of consumers. Also, how many opportunities have consumer had to hear a true A/B comparison between an MP3 file and a higher-resolution format? For comparison, HDTV was a relatively easy sell to consumers because it was easy to see how much better the picture was than standard definition. Thus, consumers ponied up the money for the HDTV sets, even when they were really expensive.
Regarding the cost of entry, the high res systems and file are expensive relative to the MP3 alternatives. Additionally, one need high end speakers or headphones to fully realize the improved sound quality of high res audio. Neither speakers nor over-the-ear or on-the-ear headphones are conducive to the "music as the soundtrack of our lives" experience. For example, I've never seen a person run or lift weights while wearing $600 audiophile over-the-ear speakers.
In the end, high res audio requires a large input of money and a bit of a change in how we interact with music to appreciate. This Sony Walkman is cheaper than many other options out there, but is still several times more expensive than iPods and the like. Until consumers can readily access true A/B comparisons to hear the differences for themselves and the prices for the components becomes more mainstream, I think high res audio will continue to struggle.
