Well, there's the perennial question of "what is folk music", and the other one that's been around about as long: "what does 'traditional' mean?" My time machine is in the shop, so I can't tell for sure, but I'd guess that very little of what was being done 100-200 years ago sounds much like it does today. Consider that the bodhran, the instrument everybody loves to hate, didn't exist before the 1930s! There's some electric Celtic I love, such as Capercaillie, and some I don't much care for, but, in the final analysis, the marketplace will decide.