There wouldn't be "down the road" if the fight was lost. Willow and the not-Slayers conveniently ignore that.
No actually we don't know that, Buffy's actions threw that arguement away,we'll never know if she did something different they would have failed. Kennedy has a point it wasn't a done deal Buffy just gave up, thats kinda why she thinks its a failure. Its the opposite of everything she was trying to do throughout the year.
It doesn't but without the veil of secrecy and the ability to sire new ones, vampires are pretty much done for. As for demons, modern weapons should dispose of them more easily than Buffy can, so...Of course, all this relies on the population of the world and the people in charge to have two braincells to rub together, so I am probably giving them way too much credit. Not that this is a new issue, it's been the elephant in the room ever since the Initiative arc but now it's worse since the people should be asking the governments what they are doing t oprevent future disasters liek the one just averted.
So a bunch of Earth Wiccans are expected to have major weaponery just lying around, because its going to be so easy to get it, thats of course if they want it, or could afford it, or if its against their morals.I doubt Earth Wiccans are going to be carting around major amo, if they haven't been doing it since the begining, it would be kinda demeaning, and a pain in the ass, its not like all Earth wiccans are great muscle types either. Some slayers aren't off protecting people any more which equals more death to come from this loss. Vampires only need one to survive till magic comes back to spread like a disease, and demons are smart at least the most powerful ones are they are by survival instict going to plan ahead for survival and war.