Todd Howard has stated that bethesda will no longer make its games have a definite ending. This is a terrible choice for fallout. Without an actual ending any choices, assuming that the plethora of choices that were present in NV are preserved for 4, will be meaningless and without consequence. So, I propose that bethesda do what black isle did with fallout 2 in order to appease both sides. Make it possible to continue playing after the ending but make it non-canon. You'll be taken back and the main quest will be listed as finished but nothing will have changed in the actual world. People who want to continue to play may do so and people who want an actual ending can have it too.