FWIW I believe Ryan (most recently, timing matched with Dennards return I believe?), Wilson, and Chung have all received a lot of snaps next to DMC.
You're right about both TWilson and Chung seeing reps aside from DMcC, but that's actually a bit of a misconception about Ryan "receiving a lot of snaps."
According to Mike Reiss today, Ryan received the bulk of his snaps as the starting nickel CB, although he did line up next to McCourty as well for awhile. After all, he did play safety at times last year (sparingly), although I doubt that too many noticed. Aside from patsfanken's report, I haven't seen anything from any beat writers about Ryan taking snaps there. I'm not questioning Ken, I'm just saying that if it were that significant, I would have expected some more coverage about it.
I don't think there's anyway that L.Ryan is the full time safety, but we'll have to see. I think some of these drills are made to prepare players in case of situational matchups (with more CBs on the field in different looks) and/or emergency situations due to injury.
Belichick spoke of this topic back at the draft interview, and claimed that we'd be seeing some CB looks at safety, while referring to the fact that Ryan played there at times last year as well. I just don't think that means that he's moving to safety. He can be anywhere from CB2 to nickel back CB to safety, but I think they'll want to see him at CB for the majority of the looks, especially with Revis/Arrington's situations for next season.
Injuries will occur that will lower the number of available CBs, along with some poorer play. I think too many are looking at it from a best case scenario and trying to get Ryan on the field. Thing is, I don't believe that Belichick will have any problem getting him plenty of looks. For the season, he saw 51% last year, up to 55% if you include the playoffs.
I think the fact that we play the majority of looks in subs will allow the CB3 and even CB4 to see plenty of looks, depending on the matchup. In the meantime, I like the idea of giving other guys looks at different positions, as injuries will dictate where they line up in the regular season/post season.