Simple, Blizzard cranking out free downloadable custom campaigns pack with post-Brood War/other 2nd Great War stories back in the day or couple "Founding of Durotar" sagas to entertain the fanboys till HotS.
* Emperor Mengsk's reign with the introduction of Prince Valerian to the public eye and his Moebius Foundation etc.
* Gen. Horace late career and zerg invasions.
* Enigmatic life of our Dominion ghost Nova.
* Bring life of the Raiders' time on Deadman's Rock (ig. Matt's card game, wanted Egon Stegmann by hoodlum bosses, Graven Hill and his mercenary contacts)
* Umojan, Phash, Liberty's anti-Dominion operation.
Or some type of unique maps with brief lore details like from those old Map of the Month.