This dynamic rolls two ways.
Without the half-chance of Boise State playing Oklahoma in a bowl game (much less a BCS game), would BSU have even expanded their stadium to 30K and then 32K?
Non-BCS schools want to be associated with the BCS schools WITHOUT chasing them out. Forming their own association is always an option. If the game becomes Michigan OR NCAA, Notre Dame OR NCAA, USC OR NCAA, and so on for most BCS schools, the NCAA loses.
That's why the game is the non-BCS schools trying to primp and preen to get major college attention rather than a large number of schools taking the NCAA to court.
Actually, it might have taken a little longer, but I do think that BSU would have expanded. They're the perfect template of how to take a solid I-AA program and turn it into a solid I-A program, so it's only natural they keep expanding. I'd imagine it'll be at 40k within the next 10 years.
Actually, I think you're overestimating the clout of the BCS conferences. They also get a very sizeable chunk of money from the NCAA for March Madness, and if they decide to go it alone they take a very big hit. Dropping sports is also out of the question, because they still lose overall prestige by dropping sports (except maybe for the SEC). Not to mention say a conference has a so-so year, like the Pac-10 did this year, and arguably the Big 12 last year, the Big 10 the previous couple of years, etc, and that could seriously jeopardize TV money if they have an off year heading into contract renegotiations. So yes it is lose-lose if the BCS conferences walk away (even though the Big East wouldn't right now,after 2010 could be a different story, and I doubt the ACC would either), but the hit is just as costly for the ones who walk as it is the NCAA.