Even if a head shot from a sniper is a 1 shot kill, they have ways to protect you from it, from the before mentioned way of putting on a helmet
always a good idea. and then isn't there something like a special ability that protects you from headshots for a certain amount of time or something? maybe that was just an example of something they MIGHT have, I don't know. But I'm sure if they had 1 shot kills from sniper headshots, there would definetly be ways to counter it.
Plus there will be so many people fighting all at once, and we don't really know how the fighting will go down, if the snipers will leave a trail you can easily follow to their position, how bright a muzzle flash might be, or if there will be smoke gernades to block their sight (I hope so :D smoke gernades are awesome and can counter a lot of things on the battlefield). And we don't know how far snipers will actually be effective from.
I know if UT2K4 the shock rifle was pretty much as long as you could see the person it was 100% accurate, but people always moved around so fast and so much that if they were far away it doesn't really matter. Good luck hitting a tiny dot thats flying all over your screen
I don't think snipers shouldn't be allowed to have stealth, if people want to play stealthy then let them. Once again we don't know everything and for all we know there could be a special ability that lets you see stealthed people. or that stealth only lasts a certain amount of time, or you have to stay still to be invisible. Or maybe when you shoot you get brought out of stealth for a bit. I don't know. If anyone does, I would love to be informed :D
As for being able to sneak up behind somebody like a rogue in an mmorpg or something, i haven't seen anything about actuall swords and daggers being in the game (once again if anyone knows please tell me). It would be cool to be able to kind of sneak around and melee people to death though, with whatever weapon, even if it's just beating them to death with your huge machine gun.