47 realises that the events of the past three games didn’t truly happen he is still in Paris bleeding out on the floor in Paris having been shot by CICADA agents after trying to impersonal the Sheik. The past three games have been his dying hallucination but then it is secretly reveal that is actually a crazy dream 47 is having just before he shoots Skurky in Sledgehammer. But then it is revealed that the church is actually Purgatory and the series since Contracts has actually been a coded allegory for the afterlife
Then we hear Diana talking as it is reveal she is in her family estate writing her very own spy novel and the whole series has been fake from the very start but then we see her little writing room as a snow globe and we see Ortmeyer abusing a clone for playing with his toys.
But in actuality all of that is a dream 47 has while he is being tried in The Hague awaiting his trial for various high profile assassinations and he is put in a cell with Grey who proceeds to give 47 grief for buttoning his prison jumpsuit to the top button. But you see it is actually manic visions Diana is having after going insane and killing the ICA proclaiming herself queen of the World until 47 shoots her and then we realise Diana died of cancer and 47 is telling his kids about how he met Diana.
Oh but I am not done as it turns out CEO Arabak has snuck into the animators room and highjacked the ending. He turns to the camera and goes “Ain’t I a stinker” and then Travis drops a piano on him and goes “Winning”. Cut to credits.