Grabner is a tough one to get a fair trade out of. He definitely isn't a top 6 winger, but hes a pretty elite bottom 6 guy. Wont' make his linemates better in the slightest but hes an excellent PKer who is the master of broken plays and springing himself on a breakaway. He isn't going to be a guy at the top of any teams prime targets to trade for, but if the Rangers are making him available he is also the type of guy who can find a spot on pretty much every team out there which would drive up his eventual return.
Might return a late first if there is a bidding war, could definitely see it if Rangers add a minor sweetener with a mid/late pick. Since the Rangers are likely to be fighting for a playoff spot I think a more likely return is a cost controlled, younger bottom 6 who would be a small downgrade in the present but they would hope has more(or equal) potential down the line.