I think we've basically seen all we're going to see. The fashion will continue to ebb and flow from along the subdivision of the three models. pre-1780, post-1780 and 21Century. I see it becoming more acceptable as other artificial social barriers are broken down.
There will be extremes in length, pattern and material. We've seen that. There will be innovations. I saw R-kilts built in bottle holders and read about kilt pin grommets. The market will determine their permanence. Will the bottle holder work for everyone? The kilt pin grommet idea assumes a standard kilt pin design which doesn't exist, and our kilt personality doesn't really accept that kind of standardization. Inside apron pockets are practical for small things, uncomfortable with a wallet or knife and impractical for bottles or guns without additions support.
I would predict an evolution in computer generated patterns. The Saltire kilt is brilliant in concept and design. How compatible is the Star and Stripes in terms of people accepting it on their bums and sitting on it? What about the classic image of Che, or Marilyn, on the back of a kilt? Hmmn, Rolling Stone's tongue, bike logos, sport team logos, the Maple Leaf.