Eric's great post (below) about yardage distribution made me think about the conditions necessary for a breakout #2 WR to appear on a team.   I hope he doesn't mind, but I'd like to riff off his post.  Using the same guide as Eric, I'll consider a 1000 yard #2 WR as a "breakout" wide receiver.

Based on what has happened in the past, here is what I think is necessary (in order of importance) for a breakout #2 WR to happen:

1)    Significant upgrade in quarterback
2)    New Coach (preferably Head Coach, but other coaches help)
3)    Established #1 Wide Receiver

Going over the teams in the AFC only (for now), I see 2 teams that fit these criteria.  One team is a strong match, the other one is a long shot.  

Miami (Strong Match)
1)    Upgraded from Joey Harrington to Trent Green
2)    New Head Coach (Cam Cameron), new QB Coach (Terry Shea), new WR Coach (Terry Robiskie)
3)    Chris Chambers (677 rcv yds, 4 TD in 2006)
Potential Breakout #2 WR: Marty Booker

Houston (Long shot)
1)    Upgraded (maybe) from David Carr to Matt Schaub
2)    New WR Coach (Larry Kirksey)
3)    Andre Johnson (1147 rcv yds, 7 TD in 2006)
Potential Breakout #2 WR: Kevin Walter

As Eric says, it seems unlikely that any new 1000 yard #2 wide receivers will appear in the AFC this season.  I think it would be very unlikely that one would appear in the AFC this season outside of these two teams.