Aggra won't die. Reasoning for me to think this?
Thrall - his story was that his PARENTS died leaving him an orphan, he is now in the SAME situation as his parents were. They saw the horde going to a ruinous path. They tried to act to save it but paid the price. Thrall even had to watch his parents die during cata (caverns of time story thing).
Having his son have a repeated story of one or both his parents die would be a tad sucky. It would make more sense for Thrall to throw Garrosh off the throne and then assume control once again to come full circle and save the horde from it self like his parents had tried. Remember Thrall has never been in this position before. When he took over the horde they were weak and needed uplifting. Now they are strong but giving into bloodlust. This is the same situation his parents faced.
Also it would be nice to not mirror varians wife with aggra and having aggra die. it would make both Thrall and varian the same damn thing :/