I agree with Jock, with certain reservations. Firstly, I don't think members of a Scots clan (and just to be clear, I'm not one) will ever stop wearing it's tartan, no matter how far removed from Scotland they are. Secondly, there's the special weave issue, which creates a certain chicken-and egg situation. Which comes first, the production run or the popularity?

And then, look at the few attempts to sell kilts to the general public (or at least to punks and goths, or to fashion victims). These are always in a generic, non-registered tartan. I expect to see more of that.