Eddy for what it's worth I feel the TT would survive an exodus of top riders, it has done in the past.
Top riders do attract sponsorship which is a much better scenario for the Manx government, but it doesn't stop a large number of tourists turning up - less of course, but fans have always turned up in fairly large numbers.

In the 90s MCN, concerned at the drought of top stars, did a survey on TT passengers about their preferences to improve the event. The overwhelming majority stated seeing the machinery side of things better supported (ie more top teams) was more important to them than seeing top stars turning up. I think one attracts the other and visa versa.

I'm sure the majority of one-off day trippers want to see top stars racing, but the average hedge anorak would probably still turn up if they weren't present. I'm not saying that is a good thing, just adding some information to your post. No one has to do the TT these days, the only person I can foresee doing a boycott in the near future is you.......... to be fair that's what I thought the thread was about :-).