I'm currently playing New Vegas and loving it by the way. The graphics aren't Skyrim but still solid. My question is this, how much of a drop off in graphics do I have to look forward to when I get around to playing Fallout 3??

When New Vegas was made, they used the Fallout 3 game elements for most of it, and only added what they needed for New Vegas specific places. So, the games have the same quality. They do however have a dramatically different look and feel, but that is style more than anything else.

There are some texture mods that improve the look. I tend to use the smaller of these as even they are higher in res than stock. There are also mods that change the sky as some think it is too tinted. But, to me, that adds to the look of the game.