Might as well get one started. You can’t access the final chapter of the campaign unless you have killed Sarkareth in Aberrus. Probably a bad call on Blizz’s part since he isn’t available on LFR yet.
Edit: Just so everyone knows, this means that LFR only raiders can’t finish the campaign until the final LFR wing is released on June 20th.
Edit 2: For those that don’t want to wait a month, the link to the WoWHead article with the video and dialogue from the quest is below. SPOILER WARNING!