Mexican standoff is always fun, but I'm not sure what Fett would bring to the situation. If they do bring him back, I think it'll be for the purposes of clarifying his actual Mandalorian status. At the moment we have actual Mandalorians and foundlings (adopted Mando's), then we'll have Fett, who may be one or the other - or neither... he would also be considered dead (or still being digested in the belly of the Sarlacc) by the average RotJ viewer, and by those that have followed the books, his status would be unknown at best - but those people probably aren't expecting to see him in Mando armour. If they get Temuera Morrison back, that would be kinda cool, though might be a little confusing for those who may remember him as Jango.