Interesting question and observations.
I think that a fetish is something that is going to continue to exist. Every generation has its percentage of men who are aroused by the spectacle of two women physically competing against each other. That's not going to change. This isn't like football, which is seeing a dramatic decline in interest among the younger generations, both in participation and in fan appeal. What will change, as has been noted above, is the industry itself. How does a company capture the demand for this type of material and still squeeze out a profit? With all of the pirating and free material available, I wonder if that's going to be possible. So if the producers pack it in, where will one find material to watch? The movies?
If the only place that new catfights are going to be produced is in full length movie, then the only thing that we're going to see are the "new age" karate kicking, bloody, slugfests that we're seeing now, not the age-old hair-pulling, slapping, clothes tearing ones that followers of our fetish truly enjoy. No Crystal, no California Wildcats, etc., etc. Hence, the material that we like will only be available for viewing on free sites (like Youtube) and it will be the stuff that we've seen for years. No one will be producing any new stuff.
Oh well, times change. Just my take.