Well...Yes and no. It wasn't tested legally in court at that time so there could still be a debate whether or not a wing truly constitutes a "sail". Having it happen once before makes the proverbial bat a little bigger but it doesn't automatically hit a home run. In other words, if SDYC cheated in 1988 and got away with using the wing, it doesn't make it legal forever into the future. It does, however, offer some intrinsic evidence that rigid wings are commonly used as sails in extremely similar scenarios.

Disclaimer: I'm not saying I think SDYC cheated - In fact, I believe the rigid wing sail to be a true "sail" that will stand up to a court or international jury test if it goes that far.