Does there need to be a single canon ending? I'd like to see FO4 start out the character creation screen with a request to load an end-game save from FO3 and NV, and then base the factions and main quest line of the new game on what you did in the previous games. If it was in the games, it's canon. Why not extrapolate that idea as far as possible. Okay, obviously the answer to my question is that it would be a hideously complex task to build FO4 in such a way that it would provide meaningfully different game play based based on your previous choices...but it would be sweet. I know bioware did this to some degree in mass effect, but doing it right in fallout might be asking too much. Meh. I can dream.