Well, Taim didn't read the other books in the series so he has no reason to give a damn about it. And really, there's nothing for Rand to be too interested in there either. He demonstrates the extent of his interest when he asks if Elayne knows. That's all those people are to him - family members of the girlfriend he has been with the least. The fact that all of them have a couple of forthcoming relatives in common is unknown to any of them. Why should there be anything important here? Rand's major concern for Morgase was another one of those women-dying issues. He knew about the situation Morgase was in and ignored it and ended up hurting his girlfriend, or so he thought. Now that he's moved beyond his inability to kill women, and been made to strangle his girlfriend by one of the Forsaken, the amelioration of some very old guilt is hardly going to resonate much. Not to mention, his most significant motivation for caring about Morgase's fate involved how it affected Elayne's opinion of him, and given their last encounter, I doubt he is all that worried anymore.

In ToM with the rest of Perrin's (and Mat's) storyline. Sanderson said back when they announced the breakup of aMoL that tGS & ToM would be split primarily between two characters each. Rand & Egwene were the main characters in tGS & now it's Mat's & Perrin's turn. Presumably Elayne might play a supporting role in one of those, the way Min & Aviendha did in Rand's. This is supposed to bring all the plotlines together for aMoL. Don't be surprised if Rand & Egwene are as absent from ToM as Mat & Perrin were from tGS.

It's more like a teaser for the next book than any kind of attempt to reveal what happened. I fully expect there will be more details in ToM.