My bet would be they don't sign him. Nill let Greg Pateryn walk last season have surprisingly playing bigger minutes than expected. I would actually guess that Taylor Fedun gets a contract instead. When you consider how reluctant Nill is to waive D, my guess would be Bayreuther is in the NHL next season as well. That would leave Oleksiak, Fedun, and Bayreuther fighting for minutes on the 3rd pair.
Since Johns is a wild card, I could even see Dallas going into the season with 8D. I would like to see Tyler Myers play with Heiskanen, and I now Satan has talked about Jake Gardiner as someone he'd like to see in Dallas. That would ultimately make Johns, Fedun, Oleksiak, and Bayreuther fight for 3rd pair minutes with Johns having an upper hand assuming he's healthy.
That means the AHL next season could look something like this ....
Hanley-Cecconi
Heatherington-Hansson
Nyberg-Gleason
That said, 2016 pick Jakob Stenqvist might come over to North America next year, He played so well in Traverse, he was a surprise addition to the NHL training camp roster. He's had another good year in the Allsvenskan, but Dallas does have one more year to sign him, and they could want to see him in the SHL next season.