In Minecraft: XBox 360 Edition, There is an option to reset the Nether. What does this do? Does it generate a "brand new" Nether with a completely different layout, or the same Nether with some additional features?
The option does build a new Nether, but the more important thing is that it applies all new changes to it like Nether fortress with blaze spawner, so you can get these new materials on your old (before updates) world. As you can imagine with a new build, all the buildings/construction you have will be erased.
Reseting the nether will create a brand new nether. Doing this is helpful if your nether doesn't have a nether forteress or any blazes.