Ok, so I have a theory for what the "Bomb" at Leg 8's Pit Stop is most likely going to be. Not sure if its already been said, but according to Wikipedia, there's a Fast Forward next Leg, and based on the new promo, I'm guessing it will involve shaving your head. Having seen the spoiler photos from the Final Leg, Daniel & Ryan have significantly shorter hair, pretty much bald infact.
So, I'm assuming they go for the FF, and the "Bomb" will be the big (loss of hair) reveal to the other teams. This is a pretty lackluster "Bomb" if you ask me, but going by TAR Oz's history, they tend to over hype upcoming events. I.e: Leg 2's "Drama at the Pit Stop after one team breaches the rules."