Honestly, the thing that's most likely to prevent Hogan from ever coming back is his age, and even that's not a total dealbreaker. The WWE canned him to escape an avalanche of bad publicity they would've surely garnered for continuing to employ a guy who admitted to being a racist.
Cut ahead five years - let's assume Hogan keeps his head down and out of trouble, and stays in shape. Is it so outlandish that Vince or Stephanie or whomever is running Creative wouldn't see money-making potential in bringing Hogan back for a short run?