If you can handle New Vegas, you should be able to handle Skrim, that's my guess, at least.
Either way, you could always customize the graphic settings to play on your rig.
And going by the level of detail I saw in GI, I'd say at most you'd need a gaming computer that would probably cost, by the time Skyrim's released, anywhere between $900 (for just plain being able to play it may be on medium) to 1500 (for high to best graphics). Any higher than that then you're buying pre-made, which is stupid unless it comes from certain sites that build computers the way you want them, or you're trying to put all of the best hardware into one system.
$900 - $1500 would be a price I'd expect to see for a premade, not one you'd build yourself. For ~$600 you can build a kick-ass rig.