I don't think it's a matter of technology, but of sound. Advancements in technology can improve certain aspects of a design but is hardly the benchmark of what will sound good. After all, what real advancements in dynamic headphones have there been of any real note in the past 20 years? Lighter, stiffer cones, different voice coils, stronger magnets... not a lot really. Stat technology may have peaked already as they have probably reached a stage where vast improvement in the basic component design is near impossible, what it comes down to now is modifying the shape, housing, amping etc. to tune the sound. That they may have peaked technology-wise means little when that technology is still and will remain very high.
Dyamics have improved a lot over the years to the point where they are in some instances the equal to a good Stat, however, that number is still very small and sometimes costly when you sit down and think about it. The vast sea of headphones available are still fairly poor to average at best.
The top models of the top makers, that number is very small when you relise how few makers there are that put out top quality 'phones. Stats are still very relevant these days despite the advances of dynamics. As long as Stax and Koss keep making them that is. I would love to see more makers put out electrostatics as they are a very stable and well tried technology that can deliver truly world class sound.