If Gronk was out for the year, I might feel bad for NE, but "possibly" missing the "start" of the season isn't quite as worthy of the overreaction. Also, I don't believe New England's chances of a fourth title, even with a healthy Gronk were high enough to perform a nose dive. A puddle jump...maybe.
How much higher than this do you want them?
http://www.ibtimes.com/super-bowl-2014-betting-odds-new-england-patriots-san-francisco-49ers-favorites-win-title-1120881#Granted it these aren't the most recent. The more recent ones take in to account Gronk. They haven't exactly nose dived but they have declined from the #1 spot.