WWG is trying not to spoil too much for the finale, that's why for this chapter he went from three teaser posts per month down to two. He said that every major event has been teased now, but that he might do a teaser salad in the future.
Even with the reduced frequency of teasers, we've already got WAY more teasers compared to recent chapters (see my count below). I take that as a good sign that Chapter 13 will have a ton of content, especially if much of what happens has been kept a surprise.
Chapter 10 - 116 teaser pics
Chapter 11 - 119 teaser pics
Chapter 12 - 163 teaser pics
Chapter 13 - 239 teaser pics