I see your point. But Edler is a borderline top pairing D signed for 3 more years. He isn't exactly young but he won't even be 35 at the end of the 3 years. Not a geezer either.
You could interpret the trade as "for now and the future" if Murray's looking 2/3 years down the road and not necessarily 5/10.
Don't have room for anyone with a NTC and Carrier has been Buffalo's best player the past few games. He looks like he could be a fairly nice piece for the future and Murray has already wasted a lot of futures in his attempts to speed up the rebuild.