I'd like to see it too. Most hardcore boxing fans would, though I don't think it is a fight that will sell to the masses very well and they don't necessarily need each other to finish with strong legacies at their respective weights. It's probably a moot point since it won't happen, but I think GGG actually has more to gain and Ward more to lose. If G were to beat Ward convincingly it would be the victory that catapults him to that level of greatness that has eluded him. If Ward wins it might be a case of people saying that GGG was too small for him and was over hyped to begin with. Plus, the age discussion will come into play the more time that passes.
It's not going to happen. Both fighters don't need each other. They have enough opposition at there respective weight classes