There will likely be some upgrades to the engine, so it will look a bit better than Fallout 3 and Oblivion, and they will also likely make it semi-scalable so that it looks better on PC than it does on the 360. But the reality is that the PC market isn't that big any more, so they aren't going to spend a fortune doing lots of extra work especially for the PC.
So yeah, it will no doubt look really good, but when I see people posting pictures of real photographs and expecting it to look similar, you are only setting yourselves up for disappointment. Same goes for upgrading your PC components. My other PC still has an 8800GTX which is about 3.5 years old and it still runs 99% of games cranked. The only ones it struggles with are PC exclusives (Arma2, FSX, etc). The fact is, the crapbox360 is holding back progress of gaming graphics, and this game will be no different.