At first glance this looks like a tough spot for three rookies, and a 2011 practice squad member (Ross) who's had zero regular season experience. Unless Hayward is a complete disaster in training camp, which is very unlikely, he'll move into the spot vacated by former Packer Pat Lee, who's now with the Raiders.
Then it comes down to whether one of the three undrafted free agents (Merrill, Ross, Turner) can move ahead of House. While the most likely result is that they're only competing against each other for a spot on the practice squad, the fact remains that House was given zero opportunities last season while the secondary was imploding. If House struggles during the preseason, he could have reason to worry.
But other than a possible competition for the final spot on the 53-man roster, the depth chart should remain the same. Woodson is back, and Bush was re-signed to back him up. Shields took a big step back in 2011, but he played with the first team defense during the open OTAs. Some concern remains about whether Williams is fully recovered from his shoulder injury, but his injured nerve will heal at some point and he kept his starting job throughout 2011 despite his bad shoulder.
Overall competition level: low. Other than a potential battle between Shields and Hayward/House/Bush for the nickelback, there shouldn't be too many surprises here once the longshot, undrafted undrafted cornerbacks fail to move up the depth chart. The cornerbacks need to play a lot better in 2012, but that doesn't mean that there will be a lot of changes to the roster.