As a Rangers fan I'm pretty confident that Hayes isn't getting a 1st and a top organizational prospect as a rental, but a 1st and a B prospect is totally realistic. Hayes is good defensively, drives offense, plays both special teams, and brings size down the middle of the ice. He's also having the best season of his career. Those factors will make him a very attractive piece for a number of teams.
I also anticipate the Rangers trying to work a deal where Hayes extends with the team he's dealt to, or at the very least insisting on a conditional pick being included to satisfy that case.