The reason I ask, I'm rereading FOTR. In two passages there is some foreshadowing of it, even beyond Aragorn's warning. First when Gimili says he needs no map to identify the mountains, and looks forward to seeing the Mirrormere. In response, Gandalf says I hope you have joy at the sight of it. Second, more ominous, while in Moria, Merry and Pippin run ahead. Gandalf says, you should let your guide go first while you still have him.
I had always assumed Gandalf took Aragorns warning seriously, but still believed he had a chance to make it through. Now I am not so sure. What does everyone think?
Edit:
I am greatful for the learning of the wise. I have been duly corrected in my error and repent of my folly.
Unfinished Tales expands on and sheds a lot of light on various things from the legendarium and most of it is generally considered canonical. What things from HoME would you put in that same category?