>>717290718
They probably didn't even think of it. All romance written by Blizz in the last years has been incredibly artificial and formulaic. "Here's your designated spouse" a la Thrall.
The bond between Anduin and Sylvanas developed in a fairly unexpected, unconventional manner, which leads me to believe it was completely accidental and Blizz never thought of developing it further than SL and Sylvanas' book.