How did you come to the conclusion that he, specifically S. Hawking, does make such a prediction ? The reason I am asking is that S. Hawking likes bets, and as far as I remember, has an estimate of less than one percent probability that the LHC will produce black holes, although the other scenario would probably give him a Nobel prize.
When I saw Lisa Randall's lecture Warped Extra-Dimensional Opportunities and Signatures, she made it clear it was unlikely : one needs to really adjust the models and at best gets close to the production threshold. The reason it is important to investigate is that the signature would be pretty clear and it would it be a shame to miss it !