Brook may well do a Calzaghe on him but I dont want to wait till Porter is 40something before they fight do you.
It wouldn't be as big of an upset as Honeyghan v Curry. As it's already been mentioned, Curry was considered #1 P4P at the time, nobody gave Honeyghan a hope. Brook on the other hand, although he might be the underdog there's plenty of people out there that will be backing him to come out on top.
Curry was (wrongly with hindsight) considered by some the best fighter in the world at the time. Some were even saying he could be the one to end Hagler's reign. Porter looks a superb prospect, but I doubt even his biggest fans are calling him the best fighter on the planet. I think this is a classic pick'em, with any advantage going to Porter because it is in the States. Curry/Honeyghan was a mismatch at the bookies; Curry was 1/6 in the UK, so I am guessing at least 1/10 in Vegas/Atlantic City...