He'll definitely be around Sansa again, that's half the main point of his arc, to restore her faith in the idea of a true knight (Elder Brother was knighted, he'll knight Sandor) having been the one to tear it down.
I think he'll kill UnGregor but it will be for a greater purpose. The Elder brother said the Hound lived only to kill his brother, a tormented and twisted existence, if Sandor hears Gregor is back and rushes off to kill him then he hasn't undergone any character growth, more likely killing Gregor's undead form will be like a mercy setting Ungregor free.
Maybe the super healer on the Quiet Isle can cure his leg and facial scars, when Sandor comes back I don't think he's going to be immediately recognisable to Westeros.
His list of shit to do I think is brave dragon's fire, kill Corbray and defeat Ungregor.