He's not going spoil something Jordan has placed in the story by book 4, as sometimes alluded to again, but has not yet revealed. Jordan clearly wanted us to keep wondering if those questions were important, or he would have revealed them long ago (some even argue that all of Rand's questions have been revealed, that how to win TG and how to survive were two questions, and the third was how to cleanse saidin. Brandon knows a lot of fans speculate these answers will be important - and they are part of the mystery he built around Moiraine with the foreshadowing that without her Rand had almost no hope to win, so don't expect him to reveal now if they're right this plays a part in the story or shatter their theories by admitting those answers were a red herring and won't surface in the last book. He'll give the same answer we would have gotten by RJ for this: RAFO or something as evasive.

Brandon dislikes spoilers, and Harriet is allergic to them and even more close-mouthed than RJ was. There's really not much Brandon could reveal about the three books before publication. Heck... even after Tor had put the cover blurb for TGS in a trade catalogue, Brandon remained unwilling to even say during Q&A that the two characters the book focussed on were Rand and Egwene. He rafoed all questions in the vein of "will Lan, Loial etc. be in the book, so imagine a plot point he knows many have built expectations about... The times Brandon was asked questions like this, his answer was something like "RAFO on what RJ would or wouldn't reveal. " (it's a real one, the question was if we'd learn more about Farstrider in AMOL or he wouldn't be mentionned again.)