Given all of the things that they need to address in the 10-episode Season 5 before the show ends, not to mention all of the extra characters announced (Man-Bat, Lady Shiva, Mother and Orphan, The Ventriloquist, potentially Calendar Man, ETC), I don't think there is any room for them to develop Harvey Dent into Two-Face.
It would also be somewhat refreshing to see a single major villain (in this case, Harvey Dent) not to turn into their supervillain counterpart before Bruce Wayne is Batman. However, here is what they absolutely NEED to address in the final season:
• What happened to Harvey Dent's partner that led to his anger problems? This mystery was briefly set up in Season 1 and was never mentioned again.
• They need to explain all of the Thomas Wayne stuff from Season 1-2. Why did he have an armoured vest with a bullethole in it? What else was on that computer besides Pinewood Farms? What else did he do that led to him getting killed? There's also a lot left unexplained about the Arkham Plans and the larger Wayne projects from Season 1.
- • They should just fill in all of the gaps between the Wayne murders, Arkham plans, Pinewood Farms, the computer and bullet proof vest from the proto-Batcave, and the Court of Owls.
Those are really the two biggest loose ends that I can think of that they absolutely NEED to address. Hopefully they didn't forget about that stuff.
It would be awesome if the final season went back and checked in with all of the previous villains (Dollmaker, Copperhead, Flamingo, Electrocutioner, Clayface, ETC), but with an already overstuffed 10 episodes, I've pretty much accepted that it just isn't going to happen. Still, there are a lot of smaller questions that I would love to see answered, like:
• What happened to Montoya and Allen? Where the hell have they been?
• Nathaniel Barnes' fate. Was he cured in time, or is he forever doomed to be The Executioner? Maybe he's living a life of regret now.
• Is the Court of Owls permanently dismantled, or are they licking their wounds? Have they started resurrecting dead Talons yet?
• Is the real Professor Pyg still out there, or did the assassin Lazlo Valentin completely fabricate the role by himself?
• What's the status on Viper/Venom?
• How is Richard Sionis related to the origin of Roman Sionis/Black Mask? Also, it would be great if they confirmed that Lester Buchinsky is Jack Buchinsky's brother (as many of us suspect).
• Is the show's version of Tommy Elliot destined to become Hush?
• The fate of the Order of St. Dumas. Maybe they could kill two birds with one stone by revealing that they're at war with the Court of Owls and League of Shadows, or something.
• Jervis Tetch embraces his Alice In Wonderland persona. Penguin gets his tophat and monocle, becomes trusted by the public again, and begins concealing weapons in his umbrellas.
Did I miss anything?