Okay let's sum this up: NO-one absolutely no one, despite technology, numbers, organization, magic or other superpowers is able to even hurt the shades, except for salmon and leroy.
If the shades are not going to be destroyed, they will destroy everything else (at a blinding pace, including all sovice that try to come near them). And there wouldnt be any future that salmon could have come back from.
That is why Salmon has to kill the Shades. They're number one priority for the sake of anything that is alive, undead and/or animated in any other way, unless its some form of demon. Though most of these will be gone too.
So Salmon will fight the shades and beat them, the UNA subsequently taking over the world founding the prerequisites for FI.
That way we get salmon's future (which then probably come after FI) and FI to match somewhat, and the FFF plot closes like a plot should.
That'd be one hell of a can.
And no.