Absolutely not. One thing people seem to forget regularly is that BJ Penn never turns down fights, and in doing so he does the exact opposite of what every single fighter in the UFC does. I'm not taking anything away from Rory, but in reality what happend last night was a middle weight beat up a lightweight.
Every fighter, and namely every champion except Junior Dos Santos cuts down crazy weight to fight men that are hopefully a little smaller than them. BJ, does exactly the opposite looking to challenge himself.
Having said that though, the answer to your question is NO, hell no!! BUT... I think it would reasonable for the UFC brass to tell him his next fight, and the rest of his fights have to be at 155.