Personally, I think they have more upside on defense right now than at forward. That's why it's an interesting question to me, because if you sign a top-4 D, they could become redundant within a year. I don't think it's super likely that McCann or Kahun would make a top-6 winger redundant, but I would be surprised if Pettersson and Marino don't make the #3D redundant.
That's a very good problem to have, when most top 4D are worth more than top 6 wingers. Besides... we have F depth to compensate for someone getting hurt. We still lack quality D depth options on the blueline. If we sign a top 4 guy and MP/JM make him redundant within in a year, then that bodes very well for our blueline.
There's also the fact that picking up skilled F help at the TD isn't all that expensive (usually), compared to what a skilled top 4 D would cost. Mojo went for a 2nd+4th. Not cheap, but not really all that expensive either.