I am not so sure about the "badge" meaning it has been over that trail. i have heard that many times and its always been proven as a myth. the criteria for the badge are spelled out on the jeep web site....i dont think it mentions the rubicon trail.
I do know a few years back there was a company that took a stock xk on the rubicon trail. from the article and photos posted at that time the XK made it...just had lots of body damage. I think that is the case with any 4x4 and 4x4 trail....its not usually a question of making it...its how much damage will you have.