Apparently, Belichick has moved on, although Wilson could still make the team. We have McCourty, Harmon and Ryan as our safeties. Belichick even brought in a #4 in Chung (starter for Philly, #4 for us).
First don't assume that Ryan is a "safety" just yet. Like I've said before, don't get too caught up in labels this year, they aren't going to mean as much as in the past. I think we will see a lot of so called CB's playing back in the middle this year.
As for Wilson, I think he was less of a desperate shot in the dark by BB, than an acknowledgement of the new normal in the NFL pass game. The passing of the position torch from the typical strong safety skill set of the 1990's, to a S who is as much a CB/cover guy as a straight up S.
In the past the typical "SS" was a guy who was a big part of run support and needed the skills to function as such. But when teams pass 2/3rds of the time, there is less a need for that. Now both S's have to cover well. In picking Wilson, BB was hoping he'd find a guy who could be tough enough to function "in the box", but have the coverage skills to stay with receivers all over the field. In other words a guy who Steve Gregory's mind, only with a quicker more athletic and stronger body.
Wilson, IMO, had a fine rookie year. The only issues he had were the couple of times he made some bad reads and was beaten in the play action passing game. I have no idea why he didn't seem to progress in his 2nd year, but I would guess it was a combination of making mistakes during TC, and then losing confidence. The kid has a nose for the ball. He has 5 picks in 2 years of very limited playing time. He was a fine special teamer last year, and I have some hope for him (albeit not a lot) this season. Its way too early to simply write him off (much like most were doing to Edelman this time last year)
But I digress (what's new). The key point is that BB seems to want Safeties who also have CB skills. Thus we have McCourty, Wilson, Thomas, Ryan, Harmon, and even Chung (IIRC) who have all spent time at the CB position, and will be working as "safeties" this TC. Its why I'm more adamant than ever that our secondary will be made up less of CB's and Safeties, and more by "just" assorted DB's in various configurations.