F3 did it better then F:NV IMO. Everything was scaled, but there was always a minimum and maximum level in every location so difficulty varied from place to place. You won't be able to survive long with a low level characters everywhere but neither will EVERY enemy be on your level.

Problem with that in FO3 was that suddenly molerats kinda died out and was replaced by an army of yao guai's, making the gameworld very... Strange... Like, it didn't make sense at lvl 20/30 because of the level enemies.

I doubt they will include level scaled quest rewards except money, potions and similar minor lot.
One interesting comment was that quest giver at least in the radiant story quests would not say that he gave to you. One solution is that minor artefacts/ named items is in a sort of levelled list, as reward you get an fitting item from the list, an old warrior might give you a sword, a commoner a ring or enchanted clothing.

No idea how they solve this with major quests, hopefully with skill or level requirements.