I think he could be the expendable one. We currently have 2 offensive RHD regulars (Byfuglien, Bogosian), Postma is now getting a shot, Redmond will get his soon, and Trouba hanging in the background. All 5 of them are RHD with offensive skill.
In the future I'd love to have Buff, Bogosian, and Trouba on our right side. Demand is always high for offensive RHD, so I can see Postma being trade bait, especially if he has a good year. I don't see him sticking around long term.
With the acqusition of Schultz i don't think Potsma is as desirable a pick up as when i originally posted this thread but i'd still offer a 2nd probably. That is some solid depth on the right side, something's going to have to give.