The traditional "sophomore slump" is due to one of two things: relaxation on the part of the player, who believes he no longer has to work as hard and opposing teams scheming a way to counterattack their particular skill set.
The first reason just really cannot apply to Wilson because it is not in his makeup to ever believe he no longer needs to be better.
As far as the second reason, every time in his career (college and last year) that a problem has been identified that lets the opposing D have an angle to attack, he studies it and finds a way to counter it. I see no reason that will change now. What one hears now is that D coordinators will find a way to counter the read option because of Wilson and the other young QBs using it. However, the RO is only a small part of the offense and in no way defines Wilson's abilities as a QB. His quickness, fastness, awareness and arm, combined with the addition of Harvin to his target list are going to be extremely difficult to scheme against.
If the 'Hawks regress this year (which I seriously doubt), it won't be because of a Russell Wilson slump. I am not sure the guy is capable of a real slump because challenges just make him better.