Don't know why that has to be a spoiler. :P
I have a feeling that I'm one of the few people actually watching these episodes as they premiere and not beforehand via the internet. It seems most of you folks are doing the latter. I'm not going to launch into that whole diatribe again but I'll simply make you aware of that fact in an effort to avoid spoilers.
Anyway, I was about to completely echo what Halibut just said. He took the words right out of my mouth. And, although as I watched I didn't know if Dipper would make the revelation, I said to myself, "Well, whenever he does, Wendy'll probably just be all, 'Well, duh, I knew that all along.'" And I was right.
I was yet again slightly disappointed by the lack of progress in solving the actual conspiracy. I can see now that this will likely be an arc that will play out throughout Season 2, perhaps with a few standalone episodes that have nothing to do with it (because I'm not seeing any connections this upcoming mini-golf episode would have to that plotline, though I could be wrong). I also thought when I saw the title "Into the Bunker" that this episode would be about exploring STAN'S hideout, mainly because I've heard it referred to as a "bunker" previously. But I suppose it's a little too early for that, and that's sensible enough. The time for that episode will come eventually.
There was one prediction I made that was way off the mark, though: When Dipper gave the shapeshifter-man-whatever-the-heck-it-was the journal, he had an evil look in his eye. It seems now that that's because he was actually the shapeshifter, and it turns out we still don't know who the author was. But before I had any time to think it through, a thought flicked through my mind when I saw that evil look: We've been led to think he's good. He's not. He's evil. He'll end up being the whole source of the conspiracy.
And of course, whenever we do found out who the author is, that could very well still be a workable theory; it would be a nice plot twist to implement. But that prediction's been shot down for now.