Hearns by close, yet clear decision. BHop isn't Hagler, although BHop's best chance to win is to copy what Hagler did and get inside and rough him up. Hagler had to really psyche himself up to get in the frame of mind to do that - can Hopkins do the same? Don't underestimate the Hearns left hook to the body, which he started to throw a lot more at middleweight. Shuler and Barkley are obvious examples. He would probably have more success to the body than chin with BHop, who has a good set of whiskers. If Hopkins doesn't get inside often enough he can't win, because no-one has outpointed Hearns, bar the late career aberration to Barkley.
Hopkins stops him by mid-rounds while leading on points. Hearns' jab just wouldn't work, and at mid- and close range he'd be outpunched and outfought by not too old Hopkins.
I think Hopkins has the tools to trouble Hearns though. When Hopkins goes in that steady pressure mode. I think he can slip and rush his way inside and take the attack to Hearns' body. Really banging it with those right uppercuts, and Hearns did lack an inside game and I can see Hopkins mugging him in there.
The Hearns of the Hagler fight v Hopkins of the Tito fight? I think Hearns nicks it on points, dominating the early rounds, and hanging on in the latter stages. Maybe Tommy gets a KD along the way.