It would be fair to venture that the Patriots offense is currently set. With the release of guard Chris Barker, it seems as if every positional grouping on offense is finalized for Week 1.
However, the full team is far from completed. There's no long snapper on the roster and there are only four linebackers- curious for a team that featured plenty of 4-3 fronts during last season.
The Patriots have recently signed defensive tackles Bruce Gaston and Kelcy Quarles, claiming both off waivers, giving New England a whopping eight interior defensive linemen, including rookie Zach Moore. It's highly unlikely that the team will carry all eight moving forward, and it's possible that both waiver claims were an attempt to bring the players into the Patriots organization for practice squad purposes.
As Sealver Siliga continues to get ready to play, having mostly healed from his hand injury, and as Chris Jones returns to practice (and was present yesterday), the roster spots occupied by Gaston and Quarles will likely be given to linebackers to flush out the roster.
The likely candidate to return is Ja'Gared Davis, currently on the team's practice squad, who is a fair pick to take the Patriots 5th roster spot. Additionally, special teamer Chris White still has a locker set up, so he's another candidate.
The Patriots secondary, slightly more solidified than the defensive front seven, is carrying 11 players, including the newly signed Don Jones. He will be featured on special teams, but it's unknown if he is a part of the team's long term plans. Once Brandon Browner returns after Week 4, there will be twelve defensive backs on the roster- it's possible that Malcolm Butler lacks the special teams ability to remain on the roster.
A final roster spot will be for whoever the Patriots bring in as long snapper.
My prediction is the Patriots will move Quarles and Gaston, in exchange for Chris White and a long snapper (Charley Hughlett?). I would expect Malcolm Butler to move to the practice squad in exchange for Ja'Gared Davis upon Brandon Browner's return.