So both cata and wrath had them, a monument in the main capital once the expansions final boss has been defeated. For wrath we had the fountain with a destroyed replica forstmourne, Tirion on top and some badass looking guys beneath. For Cata we had the fragment of Deathwing's jaw and either Chromie or Itharius next to it. This leaves me with a question, what is it going to be this time? Personally I have two theories:
A. If we do not kill Garrosh, I presume he will be in a cell with a NPC standing infront of him, Garrosh will curse you at interacting, and the NPC can be asked to show Garrosh's downfall (similar to the two dragons did with Deathwing and the sign Arthas), where this cell would be located, I'm unsure of, tho i suspect allaince gets one in SW and horde gets one in Org.
B. Gorehowl (implying Garrosh dies). Is put up for display in either both Org and SW, or next to his father's monument in Ashenvale, with Thrall next to them both mourning and apologizing to his brother Grom for failing with Garrosh. That is of course, only if Thrall is not the new warchief, then I may suspect Saurfang?
feel free to add inputs or contribute with other ideas