I think they said he was in to provide some spark on the powerplay. And of course to see where he's at.
I don't know but I'd imagine he gets a few more looks but he would probably need to make a pretty immediate impact on the powerplay to stay. They may give some of the other defensemen a rest game here and there to facilitate him in the lineup because he does bring a powerplay presence the others besides Pietrangelo lack.
Once Theodore comes back it gets murkier, as Theodore and Pietrangelo could be the powerplay D and they'd probably opt for Whitecloud and Korczak for their defensive play.