Leaving audiences with a WTF ending, was the strategy to get Enterprise its 4th Season, if I'm not mistaken. Throwing a Space Nazi at a still alive, somewhere in time Archer... mainly to worry CBS overlords, that this was how ENT could leave audiences hanging.
I do actually like the idea of leaving the last episode unresolved, because that's undeniable something fans of this show seem to have more than any other... imagination. Myself, I spend way too much time daydreaming about directions a 5th Season might've gone in. That in a nutshell is my problem with TATV. Finality. It's a cold splash of water that snaps you out of it. TOS didn't have that and was all the better for it. In the case of Nemesis, DS9, VOY... you also have that feeling of life goes on. To new adventures, with other days in the office yet to come... or so to speak. ENT skipped to 10 years later and decommission, with precious little to look back on and celebrate. So while in fiction, that's what the characters might've been doing in their bittersweet exchanges... reflecting on past glories, the reality was more a sense of loss for the opposite reason. Most of it was still right around the corner. They should have left it open ended, even knowing there was no chance of ever covering it.
So, no "Demons" doesn't work. It sets up Paxton's scheme to wipe out Starfleet HQ for one thing and you couldn't possibly leave it there. "Terra Prime" sort of does though and that's as good as we'll ever to a final chapter that honours the characters. What followed was clearly just so much holo dust...