A flirt of the female nightborne is "Tyrande still looks good after all these years. Know if she's seeing anyone?"
So... if she dies off in the next expansion(s) they'll have update this line or it will feel awkward.
But I don't think she will be written off. At most retired from the main scene, at most.
I only hope that she gets a better voice actress or voice direction, or both, and her lines stop being so damn awful.
They really, really need veteran professional writers/directors for WoW's lore. As far as I know the writers that write the novels have no say in the game itself. (do they?)