I don't see how any position other than QB, K, P and possibly C could be off the table. The Steelers can take their highest rated player not playing one of those 4 positions and have it be considered a good pick. There isn't a position on defense in which the Steelers can't use an upgrade except safety, but we're going to need a safety next year for sure, maybe 2.
On offense except for quarterback and center there isn't a position that couldn't use an upgrade or help based on lost free agents and injuries.
The draft is wide open for the Steelers, IMO. They will get the best player available at a position of need, it would be almost impossible to miss the target this year.