My only grouse gun for a couple of decades has been the same 26" 20ga. If I could wave a magic wand (anybody have a 28ga I can borrow?) and make them 28", I would. All the SxS's I've added since have the 30-32" barrels I prefer, but I have no intentions of changing out the little 20.
I'm not so sure the preference for longer barrels is a fashion trend. Except for the early game of skeet and .410 guns, hasn't the 26" length always been the scarcest ~ least popular in doubleguns? Maybe the move to 26" was the fad and the current love affair with longer barrels more a return to normalcy.