I agree, I don't think Sophomore slump is the right term. I don't think it will happen, but I can see scenarios where Wilson doesn't live up to the godlike expectations the fanbase is putting on him. I'm not completely convinced he is Drew Brees or Tom Brady, yet. He was hugely aided by the running game. Not that he won't be again, but I am not sure he's ready to have the whole lot thrown on his shoulders. Also, teams are going to make adjustments and attempt to make him step up in the pocket rather than allowing him to spin out of it. He just may be slippery enough to get outside anyways, but teams are going to make it more difficult. Since teams have tape on him, he's going to have to make a few adjustments. I have very little doubt that he'll make said adjustments since he is so incredibly studious, but you just never know for sure until you see it.
Contrary to popular opinion, there are still things he has to address and accomplish before he is considered one of the very best in the game. Again, I have very little doubt that he won't accomplish these things very soon. Some people just achieve.
I can't see a sophomore slump. His completion percentage should rise automatically through Harvin. The one possible pitfall could be INT's. They come in bunches for young QB's, and it wouldn't take many more than last year to put him in the bottom half of the league in that stat.
Sophomore slump? Nah. Not taking another step? Doubtful. He's going to take that next step and continue to get better, because that is what Russell Wilson does.