I cant remember but you might be able to replay the game using a final save. Just like the others. I'd know for sure if I had replayed ME3 as I did the others. So using an old (here final) save might mean restarting a game loading up the final save.
Final save lands you just before you have to jump through that gate to take your decision. Again, if I remember well. As I never watched more but one ending.
So here, for me, using a final save implies restarting the game as I dont see how they could take you out of the scene.
If older saves are available, then plugging before the leave is afforded to Sheppard should do the trick.