A banner for Obsidian's Fallout New Vegas is still the image you see when you access the age gate for the official Fallout website but once you actually reach the homepage, the five year old header no longer depicts a New California Republic Ranger, but rather Bethesda artwork used for Fallout 3.
While the image, which shows people lining up to enter a Vault, was released to mark the 2008 RPG, there's no logo, number, or title which strictly binds it to the game.
New Vegas is the most recent game in the series and is makes little sense to change it now out of the blue unless of course, Bethesda is planning to announce something; something like Fallout 4.
Bethesda has announced its first ever E3 press conference will take place this year so it seems the timing is ripe for a change. If indeed they do reveal the game in June we can likely expect another header change on the website.