You are partly correct. Kilties whose exhibition performance led to a competitive all age corps is of course is still competing. For the first couple of years it did remain alumni and all male, but it eventually led to open membership for both non alumni and women. Bridgemen are in their second year, Royal Airs existed for 3 and a half seasons.
Some of the corps are notable in that they marched/are marching only alumni for their intial year. Kilties, SCV(I think), and Madison. Unless I am wrong, 27th, Bridgemen, Royal Airs all were open from the start. I dont know about Kingsmen.