That's not how it works! You know this! There will be seperate teams for all aspects of the game. The amount of attention that the visuals receive will have no impact on the attention the gameplay receives, past the point of budgeting: how much money Bethesda invests in each aspect of the game. Considering how deep their pockets are after the combined success of Oblivion and Fallout 3, I really don't see the budget being a problem for their flagship series. Especially when gorgeous visuals sell games these days, resulting in a greater profit for every beautiful pixel.
I agree that graphics aren't the be-all and end-all, but with games like http://www.youtube.com/watch?v=1Kvl31g77Z8, http://www.youtube.com/watch?v=YkPzruS0I4U, http://www.youtube.com/watch?v=itHsEbDelbQ, and http://www.youtube.com/watch?v=a--zbG_K9kI on the horizon, all due out before TES:V, a graphics engine like Oblivion and Fallout 3's is inexcusable for such a big company. So many of you are saying that the graphics are fine as they are and don't need updating. Have you been playing games other than Oblivion recently? Uncharted 2 makes Oblivion look like it was drawn by a child. Beautiful visuals directly correlate to the level of immersion a game has, and with a role-playing-game like Oblivion immersion is incredibly important.
Part of me actually hopes they do just use a slightly updated Fallout 3 engine, just so I can see so many people contradict all their "I don't care about the graphics" elitism when the forum is filled with complaints by the very same people titled "TES:V looks ugly and outdated! Bethesda svck!" It won't happen. Todd Howard himself has stated that the visuals are the centre-piece of the Elder Scrolls series, and that he and his team will always design a TES game to blow people's minds in this department. He's the lead developer for one of the most acclaimed game development companies in the world. Believe it or not, he knows what he's talking about when he says graphics are important.