Setting is pretty cool, the technology is interesting. I hope there will be a great deal of visual variety in the game's locations. I tend to get bored of looking at the same thing pretty fast because of visual reasons, and it stops me from enjoying things I otherwise would love.
I hope there will be even more strange crazy enemies aside from the archers with the metal leg devices. I would love to have some boss fights.
Please don't make Corvo a silent protagonist, or any other variation of boring protagonist with no personality beyond just "badass hero dude". It always seems to be the "bad guy" that has the interesting ideas and philosophies, or just more relatable intellectually, while the main character is a cliche avenger/hero, but I hope it will be different with Corvo.
I wish multiplayer online shooters had interesting unique settings, and gave players crazy powers like stopping time and possession. I'm sick of all these military "realistic" war FPS, its a waste of a medium with such artistic potential. If this game is successful, please make the sequel have a competitive multiplayer component, but something that stays true to the game's assassin style (like 5 players in a large area tactically tracking and hunting each other while also evading AI city guards). This would be really nice, but I guess its not a major concern at all, I'll have Dust 514 for an online shooter to play by then (PS3 exclusive free-to-play/download MMO FPS, connected into persistent scifi universe of EVE Online for realtime economic and military interactions cross-platform, form corporations, fight on thousands of planets each with many maps for their resources, lots of guns/armors/vehicles/customization modules)
I hope the plot will be complex and multilayered. Doesn't have to be Metal Gear Solid level (though that would be nice) but make it engaging please.