I had also rather thought that Lan will die in the very last book.
On the other hand, "ch.81 of ToM" would almost be in the last third of the whole AMoL book, so to speak, thus maybe not that late.

I also think it makes sense that the Shadowspawn armies will attack in the middle/end of ToM and finally break through the Borderlands defence to attack the rest of the Westlands in AMoL (then we fully have TG).

That BS used the word "heart-wrenching" and that the content of the chapter would actually nothing to be proud about indicates to me most likely the sad death of an important good character, who BS likes, and/or a major defeat for the Light. Could also point to Noal's death during the rescue of Moriaine, perhaps (though IIRC, RJ wrote most of this himself).

We will be wiser in a few weeks!