Blood or not, there will probably be other instances in the game that will probably be more graphic and worse. BGS may allow players to turn off the blood, but I would suspect most won't.
If you mean something like the blood and multilated corpses you could often see in Oblivion, that's true, having an option to turn off blood during combat wouldn't be too hard, but I can't see us turning off THOSE things, since they'd be a part of the environment, and some might have important functions during gameplay or quests. After all, if you're given a quest to find someone and instead find his bloody corpse, you can't very well just have an option to disable the corpse entirely.
Well I haven't heard anything about beheading in Skyrim, and arrows can go through bodies without being gory. But like I said before, I'm not arguing for a removal of blood and gore, I'm arguing for the option to temporarily disable it.
I haven't heard anything about decapitations either, and you're right, you can easily have arrows going through bodies without showing blood, it looks unrealistic, yes, but that's beside the point, you can still do it.
Options to disable gore always seemed pointless to me, though, if you don't want to see some blood, than as I see it, you shouldn't be playing the kind of game that would have it. I mean, if you don't want to see blood, I understand that, but then why buy an M rated game in the first place? On the other hand, I don't see an option to disable blood and gore hurting the game at all, as long as it's off by default (Or the game asks you at the start if you want it or not.) and it does not remove anything that's actually important to gameplay, or replaces instances of gore that would play a purpose in the game's gameplay or content (Like say, a corpse that has an important item on it.) with something more tame that still gets the point across (Let's say the corpse was originally mutilated but in the bloodless version, it just becomes a fully intact corpse.) after all, we don't want people complaining about the fact that they missed out on this or that because they chose the no gore option. I know I'd never disable gore if given the choice to do so, but hey, if someone else wants to, I don't see giving them the option to do so causing any harm, so long as I get to play the game as Bethesda intended it to be played.