So, just from looking at the screenshots, it looks as if New Vegas was made from the Fallout 3 engine. They look almost identical. I'm not saying that I don't like the Fallout 3 engine, but I was really hoping that they would make a new engine. But please let me know if the two games do have different engines.
they have the same engine but a ton of different stuff to it so not a dirrect sequest to fallout 3 as like a dlc kinda however skeptisism is that fallout 4 with be all new
Plenty of other topic that would have answered this http://www.gamesas.com/index.php?/topic/1092462-what-engine-are-they-using-to-build-the-new-fallout/.