A fascinating observation.

On the subject of the Glengarry, I have always thought it a form of headwear that is much easier to wear 'properly' and so lends itself well to a uniform look readily. It seems quite difficult to get it wrong, save putting it on backwards.

The Balmoral, or tam, looks great (and, of course, has more antiquity) when nicely formed and 'cocked', but I regularly see otherwise splendid Balmorals pulled down too far, or puffed-up, or generally worn 'wrong' that I am tempted to take the wearer firmly by the neck and teach him the error of his ways..!

In fact, an ex-A&SH jock warrant officer and I had this exact discussion at the Aboyne Games recently - sloppy headwear (and there was plenty to be seen) upset his sensibilities. He expressed it differently, as you might imagine.

It will be interesting to see if, and how quickly, your predictions come true, but I can see bands swapping to Balmorals as a way of setting themselves apart from the 'old fashioned' Glengarry lot. Now you've pointed it out, I shall take note...

Incidentally, one of the trustees of the museum where I work is a direct descendant of the eponymous Glengarry himself, and has a wealth of family tales to tell.