That was the idea behind moving the BC tapings around (SD was supposed to be in Vancouver tomorrow instead with Raw in, I think, Kelowna)...since Rock would be filming in Vancouver, they wanted to get him on the show. It could happen, but you would think that if he were going to be there in any prominent way they would have hyped it last week. He could do a surprise run in for a save, I suppose, but it doesn't make sense to me that if he were going to be there they wouldn't plug it in advance.
IMDB is wrong a lot of times. Until I hear something from the trades (Variety or Hollywood Reporter), I'm skeptical. If I recall, Nash's role in The Punisher was reported by one of the aforementioned publications. I'd expect this would be similar.