I definetly going to get this game.
1) I honestly hope they keep most of the gameplay around 1500 A.D. Just because I loved knights and castles, stuff like that. Medieval stuff.
2) Black market guys need to go
3) Jannisaries (jeez)
4) I didnt care for the Mediterrainan defense stuff
5) They need more weapons and such also
6) and definitely more cities (Only Constantinople and Underworld, really?)
1) I personally like the medieval theme to it, but I would like more. But I don't want the game to revolve entirely around gun slinging. It's difficult to find a time that would have an interesting mix of weaponry aswell as be historically interesting. I mainly like the idea of the French Revolution because I like the idea of free-roaming around Paris and other cities. (Although I did this in The Saboteur)
2) The Black Market guys I agree on. They offered nothing of use in Revelations.
3) I didn't mind the idea of the Janissaries too much, but they were bloody annoying. I like an enemy who is a bit of a challenge, which is why I liked the very large bulky guys, but the Janissaries were too much and too often. Once every single guard unit has one it becomes impossible to do things like the Mercernaries Guild Challenge of getting a 5x Kill Combo on 10 occassions. Because Janissaries can't be combo-killed, only whittled down by repetetive attacks.
They obviously wouldn't be Janissaries in ACIII unless it's set in the same time period in Constantinopole, but I would like a harder opponent, but one who isn't there constantly all the time.
4) Mediterannean Defense was a sort of interesting meta-game, but at the same time, I only ever did it if I happened to see a carrier pigeon nest, in which case I'd have a fancy for it. I didn't care for taking over the entire map or keeping them in control. I wouldn't mind seeing it back, but I would be sad to see it go.
Unfortunately, it's kind of crucial to your Assassin's thing, because otherwise, if you don't use your Assassin's ever, then you've got nothing to do with them.
5) They need more weapons and more armours. And not perfect ones that I can get at the beginning of the game or what have you! In Revelations I seemed to have gotten a perfect armour set from collecting either all of the letters or going to all of the book locations. And I had done that prior to even buying all of the Tier-2 armours.
And the same thing happened with weapons.
I personally just like to stick to heavy weapons now, just because they have cooler kill-combos and actions and I love just throwing a giant halberd into a persons face.
6) More cities that you personally travel to. Assassin's Creed I was great for letting me go to Acer, Jerusalem and Damascus. I loved that. The inbetween riding wasn't always fun and I couldn't be compelled to hunt down all the flags and Templars inbetween the lands, but I enjoyed having new playing grounds throughout the game. And in ACII, I loved going to however many cities you do actually go to. I can't even remember, but I just love how I wasn't restricted and I kept getting new places with new challenges and new scenery and forms of buildings to climb and get around.
AC:Brotherhood was absolutely pissingly annoying. I've come to love it since for it's other charms, but being stranded in Rome? That is just so boring. It might be reasonably large, but that doesn't mean I don't end up finding myself in the same place again and again and again.
It's just not fun after a long time in what is a fairly small area.
And Constantinopole somehow managed to seem larger. Or maybe I just wasn't quite as good at picking out the landmarks of the area, but it was equally frustrating with not having lots of new things to see.
If there aren't more cities to travel to (Whether fast-travelling or actually riding there yourself) I will be rather upset on that front with ACIII.