There's two ways people might read this. One, Pete DeBoer wants forward flexibility and is tired of having to roll the same 12 forwards every game regardless of matchup or regardless of how they're playing. Two, the Devils don't really know how long Carter is going to be out and they can't afford to go game to game with him on the roster.
Realistically, it's a combination of both of those reads. DeBoer obviously needs roster flexibility because I can't imagine he's very happy throwing Krys Barch out every night. Also, can we just come out and call this a concussion? If it were the average "upper-body injury," then the Devils would have some sort of official timeline or timetable for recovery. Whether they'd give it to us is another matter, but they would still have known before today if Carter was going to need to be placed on IR. The good news is Carter is eligible to be activated immediately, so if he makes a sudden recovery this week the Devils would still have the option to put him back in the lineup immediately.
As for Josefson, his recall makes sense because of the very flexibility I just mentioned. Josefson can play center or left wing, the latter of which is severely lacking with both Carter and Dainius Zubrus injured. DeBoer could use him on the LW of the fourth line alongside Andrei Loktionov or on the third line in Carter's place, which is where he might fit best. Josefson is having major difficulty finishing before he was sent down, but on the third line he wouldn't be expected to do more than forecheck, occasionally come in and take draws and be sound defensively -- all of which he can do. The third line generates offense by working hard, not by scoring skill and I think he would make a nice temporary option there for as long as Carter is out. It would also allow DeBoer to mix and match Matteau and Barch on the fourth line depending on the matchup.
I would expect Josefson to be available for this afternoon's game, but we'll just have to wait and see.