It's hard to really say right now, a lot of it hinges on what the plans are with Provorov and Fabbro. I think conventional wisdom is that Fabbro is kept while Provorov isn't (whether thats via deadline trade or walk at the end of the year). They may keep both. They may keep neither. But I think Fabbro is a fit and they could use him regardless of his future is next to Werenski or not.
Obviously JJ is a one year thing. Either deadline deal or walk. I'm not sure Harris gets qualified (and I very much doubt it) with the young D in the pipeline pushing (Svozil, Hunt, etc)
Werenski is entrenched into the 1D spot.
Mateychuk is the future, and he's going to have a spot either on 2nd or 3rd pairing.
Other than that, its completely up for grabs.
Werenski-Fabbro
Mateychuk-Severson
Christiansen-Gudbranson
Hunt
That's how next years D looks currently (to me) factoring in what I said above.
Its pretty good, but could use more defensive presence. A shut down guy, which may push a guy like Christiansen or Gudbranson off the team.
Ideally, we get a 2nd pair shutdown RD to push Severson down to the third pairing. But I don't see that happening with Gudbranson still around.