If you haven't taken advantage of the buff before, or have a little bit of Black Prince reputation left to gain, then starting tomorrow you'll have the final chance before Warlords of Draenor to gain an extra 100% Black Prince reputation. The buff will run from next Tuesday through September 16th at 9am PDT.
What's interesting is that the post says "before the Warlords of Draenor" expansion. It might be reading between the lines too much, but one has to wonder if some such buff will appear as a permanent feature of Warlords. That kind of buff would make sense for older content, and follow Blizzard's paradigm of making older content and rewards much more accessible.
Blizzard's full post is as follows: