I was in Mexico after Mysterio left WCW, and before he entered the E, and he wrestled in a luche libre event, and he wasn't allowed to wear his mask then. That's sacred stuff.
There was an uproar after he began wearing his mask again. I think if he's going to wear a mask again, he has to change his name, and wear a completely different mask design. (Which he isn't doing.)
But to the topic. Not a chance in hell WWE is going to disrespect Rey by making him remove his mask. He removed it after the death of Eddie, but, remember, he had his face down the whole time, and the cameras weren't positioned to see his face. (All in respect)
I'm not even sure we'll see Rey's face in the 'E, even when he retires, and the time afterwards. I'm sure he'll be in the HoF, and he'll be inducted with his mask on.