Board Thread:Manga/@comment-31940900-20160810084407/@comment-5774380-20160811152640

They plan to destroy the Walls after they retrieve the Coordinate, that's for sure. What Reiner told to Eren was likely an attempt to convince him to go with them pacifically, but he later asked to Ymir "Do you think this world has a future?", just before agreeing that she would cooperate with them in exchange for Historia's survival (he said that Ymir herself was doomed either way, so he only could ensure Historia's safety). When they returned with Zeke, Reiner also said that he planned to fulfill his promise to Ymir, meaning he was telling the truth in that part. And yeah, Bertolt later also said to Armin "We have only two demands! We want you to give us Eren! And we want all of humanity inside the Walls to be wiped out!".

The only reason why they didn't exterminate humanity back in their first attack was because they need the Coordinate first and they could lose it in the ensuing chaos, but once they have it (and now, once they have rescued Historia and Annie), they certainly plan to wipe out all people within the Walls, which is, genocide. I don't know why this word seems to be so taboo on this wiki when it's just the reality of the situation.