I hope Fallout 4 learns from the brilliant Fallout NV. A wide diversity of endings which change for every location and major character depending on your interaction with them, a superior morality system that extends beyond the boring standard binary good/evil choices, a darker and edger theme, better character development for your companions and side content that felt more influential in the game world.
I've always had a suspicion that Fallout NV was designed to be experimental in many things it did so that beth soft could adopt the most successful and popular innovations and build upon them (I mean, weapon modding, disguises, survival stuff, faction game play, the dual morality system, the localised morality system, modular ending design etc)
Given the way they were willing to alter the leveling system in TES to include 'perks' from their experiences with FO3, because they found people liked them I think we will see adoption of some of the best and most popular features of FO:NV hopefully taken a further step.
Its nice when you see two innovative groups bouncing ideas between themselves.