So, I noticed in the opening for Tokyo Ghoul Re that they showed Kureo Mado wearing a hood, so does this mean he will return? Surely even he wasn't so deceitful and cunning that he would fake his death, go behind the CCG's back, and hunt ghouls while undercover. They also showed a hooded figure holding Amon's doujima quinque, and while they didn't show his face, I'm hoping this was him.
In the opening for Tokyo Ghoul Re that they showed Kureo Mado wearing a hood
You are mistaken, the guy wearing black hoodie in the OP theme is
Seidou Takizawa. At the end of the Owl Suppression Operation, he faced Tatara together with Koutarou Amon and was subsequently reported dead by the CCG.
As per the story in the anime, Mado was declared dead by the CCG (season 1 episode 8). Not sure if he would make an appearance in Tokyo Ghoul :Re.
According to manga
Kureo Mado is dead. He didn't make any appearance after that event, so there's no doubt that he's dead. You can also confirm from the wiki