they shouldn't concentrate too much on the graphical side of the game, imo.
They should keep to a high standard of graphical shinyness, but concentrate more on the gameplay, the lore, the unique wildlife, the quests, etc. They shouldn't push too hard to have graphical peaks. They should advance the graphics when technology allows us to advance properly. That way, graphics slowly increase, but the game will always be packed with content.
Everyone is suggesting new methods of gameplay, new game engines, and new systems. But, no matter what, there's going to be a limit to what they can fit on discs. Even with the multiple disc suggestions, I doubt a game, for consoles aswell, will require 10 discs to install 40gb. It's just not fair to those who can't afford large hard drives. (let's not get into the console/pc bashing)
When we have 40gb discs freely available at decent prices, sure. Give us a photo realistic world. But don't waste everything on graphics. Also, the game looks far better when there's uniqueness to the game. imo, Morrowind looks far better than Oblivion because it's so unique and cultural. Looking good =/= high poly-count.
... I might take this to the suggestion thread