In patch 5.3, we're getting four new scenarios -- three of which are interesting from a lore perspective, and one of which, Battle on the High Seas, is just a rollicking good time. There aren't any lore reveals. There's nothing in the scenario to further the story of patch 5.3, or lead into patch 5.4. The only thing Battle on the High Seas offers is the opportunity to smack the heck out of the opposite fashion in true swashbuckling style ... and honestly, that's more than enough reason to do it as far as I'm concerned!
Please note that this is being written from the Horde perspective of the scenario. I'm assuming that the Alliance side is much the same, just with a role-reversal involved.
Please note: This post contains spoilers for patch 5.3 content.