The Void =/= Jack of Blades, boys. I whipped him twice. He can bring it if he likes, but his ass should be black and blue at this point. I'm hot and bothered for The Void itself and the mystery that comes with it, not simply one inhabitant of The Void that we know like the back of our hands.I would hope to think that something like The Void would not be so shallow as to revolve around one little boss. Even if he was really cool.
Anyways, I would love if The Void was a part of Fable IV. The Court was destroyed, but that doesn't mean The Void changed at all. It's a deeply interesting side of Fable lore, and would tie the games together nicely. Compared to Theresa being nearly the only common factor, not to mention being completely vague and undeveloped, I'd say make use of all of these books for once. It's funny that they write all of these things and scatter them around of no real reason, and yet the storylines make no use of them.
The Crawler was awesome. I think I may have gone slightly meth-head on him when he mentioned The Void. I liked him as a villain, but that bit actually got me involved. Unfortunately he was not even an issue until the end of the game, though, so I don't know for sure that they will even make an obscure reference to him or The Void in the next game. Even if it does make sense and feel dark and epic to think about, they don't always build on what we feel needs to be built up. Scythe was mentioned in the letter from Rose in F2, but being the badass that he is they would obviously want to slowly erase his existence. Shining a bit of light on Theresa's dark side would open up a whole new side of the story, but that has yet to be done. Don't get your hopes up about this.
The franchise is gradually moving away from the fantasy RPG genre anyways - for all we know we could be fighting cyborg minions that bow to the Stomper of Chickens in the next installment. That sounds rather enjoyable though... so don't get your hopes up about that either.