I would like to see a very farm friendly act. Preferably no story/lore that gets in the way like we currently have (space space space space esc space space space esc.... ZZZzzz...). I want the area's to be filled with tons and tons of monsters. I want there to be plenty of actually rewarding events and alot of resplendid chests that dont get removed because "omg chests runs".
In diablo 2 there was this area just before tal rasha's tomb. With like 10 fake tombs and 1 real tomb. Each tomb was pretty huge and had quite some monsters in them. IMO i think area's like this would make excellent area's for a farming orientated game. You can have loads of area's inside a single game without needing to restart all the time to do the part you like.
I would also like something like the first area of act V in diablo II. It felt realy alive. Like something was actually happening. I know the first part of act III tried to reproduce that but it just didnt quite do it for me :\ Mostly because of the boring story that unlike what the said just gets in the way all the time. (space space space esc space space esc)). I hope they take a look at borderlands 2. You can do what ever, walk where ever and the quest giver will stalk talk to you without making you stand there and listen untill he is done talking. Heck you can often already complete the quest or just kill said annoying speaker interupting it on the spot in a nice big explosion of SHUT UP! :D:D:D
As for area's id love to see, Kurast is up there. But also a very early piece of concept art they did.
I realy love area's that look nice and feel alive (dhalgur oasis is awesome!). But at the same time i also realy love those dungeons like act I cathedral. I would be realy intregued if they can manage to make a nice looking area and after a certain event turn said area in big warzone destroying said area, setting everything on fire, have certain area's get floaded ect. and then have us undo those horrible things and eventually kill whatever evil cuased it :)