Apparently, the original post credits scene in The Amazing Spider-Man 2 was going to feature Norman Osborn's head in a jar. The character died early in the film from an illness that he spent years at Oscorp trying to cure. There might actually be plans to bring him back in future installments of the franchise, though.
It seems Oscorp is secretly keeping his head cryogenically frozen so that they can bring him back to life when technology catches up to them. There are some pretty disturbing screenshots from the scene that have leaked online.
The scene is described as showing the shadow man from the film walking up to Norman's cryogenically frozen head in a chamber and saying, "Wake up old friend."
Yikes! It would make sense if he did come back, though, if only to bring Chris Cooper back to reprise the role! That guy is such a great actor, and he was completely underutilized in the movie, so it would be great if they had bigger plans for him.
I'm not sure why the scene was cut. Instead all we got was that X-Men: Days of Future Past promo, which had nothing to do with Spider-Man. Either Norman Osborn's head has nothing to do with what is to come, or they are just waiting to make the official reveal in one of the later films. Would you like to see Norman Osborn make a comeback?