Hi all -- I'm active elsewhere in the fandom, but this is my first time posting here.
I do think the line from season 1 is interesting, and it does put Spike in play. As a Spike fan, it's the one argument about Spike that makes me nervous. As does the panel from Always Darkest.
That said, I'm not so nervous for a lot of reasons.
1. How does it work dramatically? Spike's been out of the picture for years now. Whether due to indifference or annoyance or a sense of betrayal, Buffy hasn't bothered to call him (when by contrast she reached out to Riley and tried to reach out to Angel for help). Let's say he's lost his soul or for some other random reason decided to be a bad guy. Whatever it is, it's a story that happened elsewhere. So where's the dramatic punch for having a character return in a VERY different place from where he was (Buffy's most loyal ally) late in a story where everyone and their dog seems to be functioning just fine thinking of him as a footnote to their lives. The story of Spike changing would be interesting - but it happened off-stage. The story of the impact of Spike's change can't be that interesting in a story that has shown no interest in him. Sure there'd be hurt -- but not hurt that resonates with the story we've now spent over three years setting up.
2. Don't want to put too much on this because who knows what's up with the seed, but if the Master's game is to protect the seed, then how is Spike setting up to be his warrior and Buffy's betrayer by taking Buffy *to* the seed? But who knows -- all of the exposition on all of this has been garbled.
3. But that does raise the detail that the prophecy wants this to be the Master's warrior. Angel's had more dealings with the Master and more respect for him. Spike came after the Master died, but unceremoniously disposed of the annointed one. He doesn't have much respect for old traditions and what not.
So if the betrayer (in a pejorative sense) is either vampire, I'd say it's more likely to be Angel, who for better or worse has been important to the story all along. Buffy may say she doesn't trust him. But she's shipped him off to save the slayers. He's got her heart. That's enough for some tears and Jeanty getting all upset. Why would Angel 'betray' her? Well, blurb in #38 says he's having to answer to whoever it was that sent him on his mission for having failed. Maybe he comes back with renewed energy to try to get Buffy to go back to paradise with him. Maybe he once again lets dog rather than Buffy set the agenda and comes back to kill Dawn or whatever it is that dog tells him he has to do now and that puts him at odds with Buffy. Or maybe he finds out that Spuffy is not quite as done a deal as it seems at the end of #36 and Angel acts like the 12-year old he just said he still is.
But were it not for the panel in Always Darkest, I'd say the betrayer is far more likely to be a Scoobie type, with Xander/Dawn being the leading candidates. And I don't think that the Always Darkest panel has to mean it's a vampire. Angel and Spike have always been part of Buffy's shadow self. The line in the panel is about not being able to kill what's *inside* you.
So that leads me to what I think is most likely: and that's that the 'betrayer' isn't the bad guy here. Buffy's own darkness is part of the problem. We've been flagging it all season long. It's gotten a lot of foreshadowing -- she wants to give into it. Dawn notably made a couple of references to slayers as demons. Angel can't be the righteous 'betrayer' on this account, because he's complicit in whatever has gone wrong with Buffy. But Spike could be. We've done a lot of compare/contrast on Spike and Angel that sets Spike up for the role to be the vampire self that still has a moral compass. Angel slogs along listening to voices (reminding us of the line about the moron that chaos employs, with moron or 'simple' coming up twice so far in Last Gleaming about Angel); Spike goes out and does some research and figures out what's going on. But there's still far more story-richness to be found by having one of the Scoobies step up to the plate as the righteous 'betrayer':
Way too much in the mix to make any forecasts or speculations. Dawn's keyness has been mentioned enough to matter. Xander's gun got highlighted, and guns have been mentioned enough to matter. Giles' willingness to take down a slayer has been mentioned enough to matter. The season has been far more about human-slayer conflict than vamire-slayer conflict and that gets personalized if one of Buffy's humans turns on her. I find it hard to believe that Joss would step over all of that rich story that's actually part and parcel of season 8 to get to some story about how the ex-boyfriend who's been scarcely mentioned all season long somehow went bad offstage and swooped in at the last minute to mess things up.